Class 9 · Science · English medium
Exploration: Class 9 Science companion
An interactive companion to Exploration (Grade 9 science): original explanations, simulations, worked examples and practice for cells, motion, atoms, sound, life and the Earth.
An original companion to Exploration, NCERT Class 9 Science (2026–27 edition). Official textbook ↗ ncert.nic.in
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Chapters
- ENHinglish
Chapter 1: Exploration: Entering the World of Secondary Science (Scientific Exploration)
Opening chapter of Class 9 Exploration on how science works. - ENHinglish
Chapter 2: Cell: The Building Block of Life (The Cell)
Class 9 biology chapter on the cell as the unit of life. - ENHinglish
Chapter 3: Tissues in Action
Class 9 Exploration chapter 3 on tissues. - ENHinglish
Chapter 4: Describing Motion Around Us
Describing motion in a straight line and in a circle (Class 9, new NCF). - ENHinglish
Chapter 5: Exploring Mixtures and their Separation (Mixtures and Separation)
Class 9 chemistry (new NCF Exploration textbook). - ENHinglish
Chapter 6: How Forces Affect Motion (Force and Laws of Motion)
Class 9 (Exploration) chapter on force and Newton's laws. - ENHinglish
Chapter 7: Work, Energy, and Simple Machines (Work and Energy)
Work is done when a force moves an object along the force, in joules; it is zero with no displacement or a perpendicular force, and positive - ENHinglish
Chapter 8: Journey Inside the Atom (Structure of the Atom)
The chapter follows the atom from an idea (Kanada's parmanu, Democritus's atomos) to Dalton's 1808 theory and then to models built on experi - ENHinglish
Chapter 9: Atomic Foundations of Matter (Atoms and Molecules)
Class 9 Exploration chapter 9. - ENHinglish
Chapter 10: Sound Waves: Characteristics and Applications
Class 9 (Exploration) sound. - ENHinglish
Chapter 11: Reproduction: How Life Continues
Class 9 Exploration chapter on reproduction. - ENHinglish
Chapter 12: Patterns in Life: Diversity and Classification
Biodiversity is the variety of life. - ENHinglish
Chapter 13: Earth as a System: Energy, Matter, and Life
The Earth works as one system of five spheres (geosphere, hydrosphere, cryosphere, atmosphere, biosphere) linked by flows of energy and matter.
Also in Hinglish
- Chapter 1: Exploration: Secondary Science ki Duniya mein Kadam (Hinglish)
- Chapter 2: Cell: Jeevan ki Building Block (Hinglish)
- Chapter 3: Tissues in Action (Hinglish)
- Chapter 4: Hamare Aas-paas ki Motion ka Varnan (Hinglish)
- Chapter 5: Mixtures ki Khoj aur unka Separation (Hinglish)
- Chapter 6: Forces Motion par Kaise Asar Daalte Hain (Hinglish)
- Chapter 7: Work, Energy aur Simple Machines (Hinglish)
- Chapter 8: Atom ke Andar ka Safar (Hinglish)
- Chapter 9: Matter ki Atomic Buniyaad (Hinglish)
- Chapter 10: Sound Waves: Characteristics aur Applications (Hinglish)
- Chapter 11: Reproduction: Jeevan Kaise Chalta Rehta Hai (Hinglish)
- Chapter 12: Jeevan ke Patterns: Diversity aur Classification (Hinglish)
- Chapter 13: Earth ek System ke roop mein: Energy, Matter aur Life (Hinglish)
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acceleration due to gravityगुरुत्वीय त्वरणThe constant downward acceleration of a freely falling object near the Earth, g ≈ 9.8 m s⁻².Ch 4 · Describing Motion Around Usaction–reaction pairक्रिया-प्रतिक्रिया युग्मThe two equal and opposite forces that two interacting objects exert on each other. They act on different objects.Ch 6 · How Forces Affect MotionalbedoThe fraction of the sunlight falling on a surface that it reflects, from 0 (reflects nothing) to 1 (reflects everything).Ch 13 · Earth as a System: Energy, Matter, and Lifealpha particleअल्फ़ा कणA fast, positively charged (+2) particle given out by some radioactive elements; a helium nucleus.Ch 8 · Journey Inside the AtomamplitudeआयामThe largest change in density of the medium from its average value as a sound wave passes.Ch 10 · Sound Waves: Characteristics and ApplicationsanionऋणायनA negatively charged ion, formed when an atom gains electrons, such as Cl-.Ch 9 · Atomic Foundations of Matterasexual reproductionअलैंगिक जननReproduction by one parent, without gametes, giving young that are copies of that parent.Ch 11 · Reproduction: How Life Continuesassumptionमान्यताSomething accepted as true enough for the job in hand, such as 'air resistance is negligible', so that a model or calculation can be made.Ch 1 · Exploration: Entering the World of Secondary Scienceatomic numberपरमाणु संख्याThe number of protons in an atom’s nucleus, Z; it identifies the element.Ch 8 · Journey Inside the Atomautotrophस्वपोषीAn organism that makes its own food, usually by photosynthesis.Ch 12 · Patterns in Life: Diversity and Classificationaverage accelerationऔसत त्वरणChange in velocity divided by the time interval; SI unit m s⁻².Ch 4 · Describing Motion Around Usaverage speedऔसत चालHow far an object goes altogether, divided by the time it takes.Ch 4 · Describing Motion Around Usaverage velocityऔसत वेगDisplacement divided by the time interval; it has a direction.Ch 4 · Describing Motion Around UsB
balanced forcesसंतुलित बलForces on an object whose net force is zero, so together they cannot change its motion. If the net force is not zero, the forces are unbalanced.Ch 6 · How Forces Affect Motionbinomial nomenclatureद्विपद नामपद्धतिThe system of giving every species a two-part scientific name: genus and species.Ch 12 · Patterns in Life: Diversity and Classificationbiodiversityजैव विविधताThe variety of life: different kinds of organisms, the differences within each kind, and the variety of habitats.Ch 12 · Patterns in Life: Diversity and Classificationbiodiversity hotspotजैव विविधता हॉटस्पॉटA region with very many endemic species that has already lost most of its natural habitat.Ch 12 · Patterns in Life: Diversity and Classificationbiogeochemical cycleजैव-भू-रासायनिक चक्रThe repeated movement of an element such as carbon or nitrogen between living things and the air, water, soil and rocks.Ch 13 · Earth as a System: Energy, Matter, and LifebiosphereजैवमंडलAll living organisms together with the places where they live.Ch 13 · Earth as a System: Energy, Matter, and LifebuddingमुकुलनAsexual reproduction in which an outgrowth of the parent grows into a new individual and separates, as in yeast and Hydra.Ch 11 · Reproduction: How Life ContinuesC
cationधनायनA positively charged ion, formed when an atom loses electrons, such as Na+.Ch 9 · Atomic Foundations of MattercellकोशिकाThe smallest unit of structure and function in living things.Ch 2 · Cell: The Building Block of Lifecell membraneप्लैज़्मा झिल्लीThe thin, selectively permeable boundary of every cell, a lipid bilayer with proteins.Ch 2 · Cell: The Building Block of Lifecell wallकोशिका भित्तिA rigid, freely permeable layer outside the membrane in plants (mainly cellulose), fungi and most bacteria.Ch 2 · Cell: The Building Block of Lifechemical bondरासायनिक आबंधThe force of attraction that holds atoms or ions together.Ch 9 · Atomic Foundations of Matterchemical formulaरासायनिक सूत्रSymbols and subscripts showing the elements in a substance and their proportions, such as H2O.Ch 9 · Atomic Foundations of Matterchromosomeगुणसूत्रA thread of DNA and proteins in the nucleus that carries genes.Ch 2 · Cell: The Building Block of Lifeclassificationवर्गीकरणSorting organisms into groups by shared features and relationships.Ch 12 · Patterns in Life: Diversity and Classificationcloneक्लोनAn organism that is genetically identical to its single parent, made by asexual reproduction.Ch 11 · Reproduction: How Life Continuescoagulationस्कंदनMaking tiny suspended particles clump together, often by adding a coagulant such as alum, so that they settle.Ch 5 · Exploring Mixtures and their Separationcollenchymaकॉलेन्काइमाA simple tissue of living cells thickened at the corners, giving flexible support to stems and leaf stalks.Ch 3 · Tissues in ActioncolloidकोलॉइडA heterogeneous mixture with particles of about 1 to 1000 nm that stay spread out and scatter light.Ch 5 · Exploring Mixtures and their SeparationcompressionसंपीडनA region of a sound wave where the particles are crowded together, so the density is higher than average.Ch 10 · Sound Waves: Characteristics and Applicationsconcentrationसांद्रताHow much solute there is in a stated quantity of solution (or solvent), often given as a percentage.Ch 5 · Exploring Mixtures and their Separationconnective tissueसंयोजी ऊतकTissue whose cells lie in a matrix and which joins and supports other tissues, such as blood, bone and cartilage.Ch 3 · Tissues in Actioncontact inhibitionThe stop in division of animal cells once they touch their neighbours; cancer cells lose it.Ch 2 · Cell: The Building Block of Lifecontraceptionगर्भनिरोधनAny method of preventing pregnancy, such as condoms, pills, a copper-T or surgery.Ch 11 · Reproduction: How Life Continuescovalent bondसहसंयोजी आबंधA bond formed when two atoms share a pair of electrons.Ch 9 · Atomic Foundations of MattercryosphereहिममंडलThe frozen water of the Earth: glaciers, snow, sea ice and polar ice caps.Ch 13 · Earth as a System: Energy, Matter, and Lifecrystallizationक्रिस्टलीकरणSeparating a pure solid as crystals from its saturated solution, usually by slow cooling or slow evaporation.Ch 5 · Exploring Mixtures and their SeparationD
differentiationविभेदनThe process by which new cells stop dividing and take on a permanent shape and function.Ch 3 · Tissues in Actiondisplacementविस्थापनThe net change in position between two instants: a straight-line distance with a direction.Ch 4 · Describing Motion Around Usdistance travelledतय की गई दूरीThe total length of the path an object covers, whatever its direction. It has magnitude only.Ch 4 · Describing Motion Around UsdistillationआसवनBoiling a liquid out of a mixture and condensing its vapour back into a pure liquid in a separate vessel.Ch 5 · Exploring Mixtures and their SeparationE
echoप्रतिध्वनिA reflected sound heard separately, at least 0.1 s after the original.Ch 10 · Sound Waves: Characteristics and Applicationselectromagnetic spectrumविद्युत-चुंबकीय स्पेक्ट्रमThe full range of electromagnetic waves, from gamma rays (shortest) to radio waves (longest).Ch 13 · Earth as a System: Energy, Matter, and Lifeelectronइलेक्ट्रॉनA very light particle with a charge of -1, found in the shells around the nucleus of every atom.Ch 8 · Journey Inside the Atomelectronic configurationइलेक्ट्रॉनिक विन्यासThe way an atom’s electrons are distributed among its shells, written shell by shell, e.g. 2, 8, 1.Ch 8 · Journey Inside the Atomendemic speciesस्थानिक प्रजातिA species found naturally in only one region of the world.Ch 12 · Patterns in Life: Diversity and Classificationendoplasmic reticulumअंतर्द्रव्यी जालिकाA network of membrane tubes and sacs that makes and carries proteins (rough ER) and lipids (smooth ER).Ch 2 · Cell: The Building Block of Lifeenergyऊर्जाThe capacity to do work, measured in joules.Ch 7 · Work, Energy, and Simple Machinesepidermisएपिडर्मिसThe outermost protective layer of cells of leaves, stems and roots, often coated with a waxy cuticle.Ch 3 · Tissues in Actionepithelial tissueएपिथीलियमी ऊतकTightly packed cells that cover the body and line its organs and tubes.Ch 3 · Tissues in ActionestimateअनुमानA rough value worked out with sensible round numbers, good enough to judge whether an answer is reasonable.Ch 1 · Exploration: Entering the World of Secondary Scienceeukaryoteसुकेंद्रकीAn organism whose cells have a nucleus enclosed by a membrane.Ch 12 · Patterns in Life: Diversity and Classificationeukaryotic cellयूकैरियोटी कोशिकाA cell with a membrane-bound nucleus and organelles, as in plants, animals and fungi.Ch 2 · Cell: The Building Block of LifeeutrophicationसुपोषणOver-enrichment of a lake or river with nutrients, which leads to algal blooms and a loss of dissolved oxygen.Ch 13 · Earth as a System: Energy, Matter, and Lifeevidenceसाक्ष्यObservations and measurements that support or contradict an idea.Ch 1 · Exploration: Entering the World of Secondary Scienceexternal forceबाह्य बलA force on a chosen system from something outside it. Forces between parts of the system are internal and cancel in pairs.Ch 6 · How Forces Affect MotionF
fertilisationनिषेचनThe fusion of a male gamete with a female gamete to form a zygote.Ch 11 · Reproduction: How Life ContinuesforceबलA push or a pull on an object that comes from its interaction with another object. It has magnitude and direction.Ch 6 · How Forces Affect Motionformula unit massसूत्र इकाई द्रव्यमानThe mass in u of one formula unit (the simplest ion ratio) of an ionic compound, found by adding atomic masses.Ch 9 · Atomic Foundations of Matterfossilजीवाश्मThe preserved remains or trace of an organism that lived long ago.Ch 12 · Patterns in Life: Diversity and Classificationfrequencyआवृत्तिThe number of complete oscillations per second, written ν; SI unit hertz (Hz).Ch 10 · Sound Waves: Characteristics and Applicationsfrictionघर्षणThe force between two surfaces in contact that opposes their sliding over each other.Ch 6 · How Forces Affect MotionfulcrumआलंबThe fixed point about which a lever turns.Ch 7 · Work, Energy, and Simple MachinesG
gameteयुग्मकA haploid reproductive cell, a sperm or an egg, that fuses with another gamete at fertilisation.Ch 11 · Reproduction: How Life ContinuesgenusवंशA group of closely related species; the first word of a scientific name.Ch 12 · Patterns in Life: Diversity and ClassificationgeosphereभूमंडलThe solid Earth: rocks, soil and landforms, down to the hot interior.Ch 13 · Earth as a System: Energy, Matter, and LifeGolgi apparatusगॉल्जी उपकरणA stack of flat sacs that finishes, sorts and packs proteins and lipids into vesicles.Ch 2 · Cell: The Building Block of Lifegreenhouse effectहरितगृह प्रभावThe warming of the Earth's surface because gases such as CO2, methane and water vapour absorb outgoing infrared and send part of it back down.Ch 13 · Earth as a System: Energy, Matter, and LifeH
heterogeneous mixtureविषमांगी मिश्रणA mixture whose composition changes from place to place, such as sand in water or oil on water.Ch 5 · Exploring Mixtures and their SeparationheterotrophविषमपोषीAn organism that takes its food from other organisms.Ch 12 · Patterns in Life: Diversity and Classificationhomogeneous mixtureसमांगी मिश्रणA mixture with the same composition everywhere, so its parts cannot be told apart, such as sugar water or air.Ch 5 · Exploring Mixtures and their SeparationhydrosphereजलमंडलAll the liquid water on and under the Earth's surface: oceans, rivers, lakes and groundwater.Ch 13 · Earth as a System: Energy, Matter, and LifeI
immiscible liquidsअमिश्रणीय द्रवLiquids that do not mix and settle as separate layers, such as oil and water.Ch 5 · Exploring Mixtures and their Separationinclined planeआनत तलA sloping surface used to raise a load with a smaller force over a longer distance.Ch 7 · Work, Energy, and Simple Machinesinertiaजड़त्वThe property of an object by which it resists any change in its velocity, whether it is at rest or moving.Ch 6 · How Forces Affect Motioninsolationसूर्यातपThe solar energy that reaches the Earth's surface, per square metre per second.Ch 13 · Earth as a System: Energy, Matter, and Lifeintensityतीव्रताSound energy passing each second through unit area held perpendicular to the direction of travel.Ch 10 · Sound Waves: Characteristics and Applicationsinterdisciplinaryअंतर्विषयकDrawing on two or more branches of knowledge, such as physics and biology, to understand one problem.Ch 1 · Exploration: Entering the World of Secondary ScienceionआयनAn atom or group of atoms that carries an electric charge because it has lost or gained electrons.Ch 9 · Atomic Foundations of Matterionic bondआयनिक आबंधThe electrostatic attraction between oppositely charged ions.Ch 9 · Atomic Foundations of MatterisobarसमभारिकAtoms from different elements whose mass numbers are equal, such as carbon-14 and nitrogen-14.Ch 8 · Journey Inside the Atomisotopeसमस्थानिकAtoms of one element that differ only in their number of neutrons, and so in mass number.Ch 8 · Journey Inside the AtomJ
jouleजूलThe SI unit of work and energy: the work done when a 1 N force moves an object 1 m along it.Ch 7 · Work, Energy, and Simple MachinesK
kinematic equationsगति के समीकरणThe equations v = u + at, s = ut + 12 at² and v² = u² + 2as for constant acceleration.Ch 4 · Describing Motion Around Uskinetic energyगतिज ऊर्जाEnergy an object has because it is moving, K = 12 mv².Ch 7 · Work, Energy, and Simple MachinesL
law of conservation of massद्रव्यमान संरक्षण का नियमIn a chemical reaction the total mass of the products equals the total mass of the reactants; matter is neither created nor destroyed.Ch 9 · Atomic Foundations of Matterlaw of constant proportionsस्थिर अनुपात का नियमEvery pure sample of a compound has its elements in the same ratio by mass, wherever it comes from.Ch 9 · Atomic Foundations of Matterleverउत्तोलकA rigid bar that turns about a fixed point, the fulcrum.Ch 7 · Work, Energy, and Simple Machinesligamentस्नायुA strong, slightly stretchy band of connective tissue that joins one bone to another at a joint.Ch 3 · Tissues in Actionlimit of resolutionThe smallest gap at which two points still look separate; about 0.1 mm for the eye at 25 cm.Ch 2 · Cell: The Building Block of Lifelongitudinal waveअनुदैर्ध्य तरंगA wave in which the particles vibrate parallel to the direction in which the wave travels, as in sound.Ch 10 · Sound Waves: Characteristics and ApplicationslysosomeलयनकायA single-membrane sac of digestive enzymes that breaks down and recycles waste.Ch 2 · Cell: The Building Block of LifeM
magnitudeपरिमाणThe size of a quantity: its number together with its unit, without the direction.Ch 4 · Describing Motion Around Usmass numberद्रव्यमान संख्याThe total number of protons and neutrons in an atom’s nucleus, A.Ch 8 · Journey Inside the Atommechanical advantageयांत्रिक लाभLoad divided by effort for a machine.Ch 7 · Work, Energy, and Simple Machinesmechanical energyयांत्रिक ऊर्जाThe sum of an object's kinetic and potential energy.Ch 7 · Work, Energy, and Simple Machinesmechanical waveयांत्रिक तरंगA wave that needs a material medium to travel; sound is one.Ch 10 · Sound Waves: Characteristics and Applicationsmediumमाध्यमThe material (solid, liquid or gas) through which sound travels.Ch 10 · Sound Waves: Characteristics and Applicationsmeiosisअर्धसूत्री विभाजनTwo divisions in reproductive organs giving four gametes with half the chromosome number.Ch 2 · Cell: The Building Block of Lifemeiosisअर्धसूत्री विभाजनCell division that makes gametes, each with one chromosome from every pair (half the body-cell number).Ch 11 · Reproduction: How Life Continuesmenstruationऋतुस्रावThe shedding of the thickened uterine lining, with some blood, when no embryo has implanted.Ch 11 · Reproduction: How Life Continuesmeristematic tissueविभज्योतक ऊतकPlant tissue made of actively dividing cells, found at root and shoot tips, in a ring along stems and at the base of grass blades.Ch 3 · Tissues in Actionmitochondrionसूत्रकणिकाA double-membrane organelle that releases energy from food as ATP by cellular respiration.Ch 2 · Cell: The Building Block of Lifemitosisसमसूत्री विभाजनCell division that gives two daughter cells identical to the parent.Ch 2 · Cell: The Building Block of Lifemitosisसमसूत्री विभाजनCell division that gives two daughter cells with the same chromosomes as the parent cell.Ch 11 · Reproduction: How Life ContinuesmodelमॉडलA simplified version of a real object, system or process that keeps only the features needed to answer a particular question.Ch 1 · Exploration: Entering the World of Secondary Sciencemolecular massआण्विक द्रव्यमानThe mass of one molecule in u, found by adding up the atomic masses of every atom in it.Ch 9 · Atomic Foundations of MattermoleculeअणुThe smallest particle of a substance that can exist by itself: two or more joined atoms with no overall charge.Ch 9 · Atomic Foundations of MattermomentumसंवेगMass times velocity, p = mv. It points in the direction of the velocity.Ch 6 · How Forces Affect MotionmyceliumकवकजालThe network of thread-like hyphae that forms the body of a fungus.Ch 12 · Patterns in Life: Diversity and ClassificationN
net forceपरिणामी बलThe single force that has the same effect as all the forces acting on an object together.Ch 6 · How Forces Affect Motionneuronतंत्रिका कोशिकाA nerve cell, with dendrites, a cell body and an axon, that receives and passes on messages.Ch 3 · Tissues in Actionneutronन्यूट्रॉनAn uncharged particle in the nucleus with a mass of about 1 u.Ch 8 · Journey Inside the Atomnewtonन्यूटनThe SI unit of force (symbol N): the net force that gives a 1 kg mass an acceleration of 1 m s⁻².Ch 6 · How Forces Affect Motionnitrogen fixationनाइट्रोजन स्थिरीकरणChanging unreactive nitrogen gas from the air into compounds such as ammonia that living things can use.Ch 13 · Earth as a System: Energy, Matter, and Lifenormal forceअभिलंब बलThe push of a surface on an object resting on it, acting at right angles to the surface.Ch 6 · How Forces Affect Motionnotochordपृष्ठरज्जुA flexible rod along the back of a chordate at some stage of life.Ch 12 · Patterns in Life: Diversity and Classificationnucleonन्यूक्लिऑनA proton or a neutron: a particle of the nucleus.Ch 8 · Journey Inside the AtomnucleusनाभिकThe tiny, dense, positively charged centre of an atom, made of protons and neutrons.Ch 8 · Journey Inside the AtomO
ocean currentमहासागरीय धाराA steady, large-scale flow of ocean water in one direction.Ch 13 · Earth as a System: Energy, Matter, and LifeorganelleकोशिकांगA structure inside a cell with a particular job, such as a mitochondrion.Ch 2 · Cell: The Building Block of LifeosmosisपरासरणMovement of water across a selectively permeable membrane from a dilute to a more concentrated solution.Ch 2 · Cell: The Building Block of Lifeovulationअंडोत्सर्गThe release of a mature egg from an ovary, usually once in each menstrual cycle.Ch 11 · Reproduction: How Life ContinuesP
paper chromatographyक्रोमैटोग्राफीSeparating the dissolved parts of a mixture as a solvent carries them up a paper strip at different speeds.Ch 5 · Exploring Mixtures and their Separationparenchymaपैरेन्काइमाA simple tissue of living, thin-walled cells with spaces between them; it stores food and may photosynthesise.Ch 3 · Tissues in Actionphloemफ्लोएमA complex tissue, mostly living, that carries food from the leaves to other parts of the plant.Ch 3 · Tissues in Actionphysical quantityभौतिक राशिAnything that can be measured and written as a number with a unit, such as length, mass, time or temperature.Ch 1 · Exploration: Entering the World of Secondary Sciencepitchतारत्वHow high or low a sound seems to a listener; it rises with frequency.Ch 10 · Sound Waves: Characteristics and Applicationsplanetary windsSteady, large-scale winds that blow between the Earth's pressure belts, such as the trade winds and westerlies.Ch 13 · Earth as a System: Energy, Matter, and LifeplastidलवकA plant organelle that makes food (chloroplast), holds colour (chromoplast) or stores food (leucoplast).Ch 2 · Cell: The Building Block of LifepollinationपरागणThe carrying of pollen from an anther to a stigma, by wind, water, animals or within the same flower.Ch 11 · Reproduction: How Life Continuespolyatomic ionबहुपरमाणुक आयनA charged group of bonded atoms that acts as one unit, such as SO4²- or NH4+.Ch 9 · Atomic Foundations of MatterpostulateअभिधारणाA basic idea taken as the starting point of a theory; it is tested through the predictions that follow from it.Ch 9 · Atomic Foundations of Matterpotential energyस्थितिज ऊर्जाEnergy stored because of shape or relative position; near the Earth, U = mgh.Ch 7 · Work, Energy, and Simple Machinespowerशक्तिThe rate of doing work, P = W/t.Ch 7 · Work, Energy, and Simple Machinespredictionपूर्वानुमानA reasoned statement, based on laws, theories, models or past data, of what will happen in a situation not yet observed.Ch 1 · Exploration: Entering the World of Secondary Scienceprokaryoteप्राक्केंद्रकीAn organism whose cell has no membrane-bound nucleus, such as a bacterium.Ch 12 · Patterns in Life: Diversity and Classificationprokaryotic cellप्रोकैरियोटी कोशिकाA cell with no true nucleus (its DNA lies in a nucleoid) and no membrane-bound organelles, such as a bacterium.Ch 2 · Cell: The Building Block of Lifeprotonप्रोटॉनA particle in the nucleus with a charge of +1 and a mass of about 1 u.Ch 8 · Journey Inside the AtompubertyयौवनारंभThe stage of adolescence at which the testes or ovaries become active, making gametes and sex hormones.Ch 11 · Reproduction: How Life ContinuespulleyघिरनीA grooved wheel that guides a rope; a fixed pulley changes the direction of the effort.Ch 7 · Work, Energy, and Simple MachinesR
rarefactionविरलनA region of a sound wave where the particles are spread out, so the density is lower than average.Ch 10 · Sound Waves: Characteristics and Applicationsreference pointसंदर्भ बिंदुA fixed point, also called the origin, from which positions are measured.Ch 4 · Describing Motion Around UsreverberationअनुरणनThe lingering of a sound caused by many reflections arriving close together.Ch 10 · Sound Waves: Characteristics and ApplicationsribosomeराइबोसोमA tiny organelle without a membrane that builds proteins.Ch 2 · Cell: The Building Block of LifeS
saturated solutionसंतृप्त विलयनA solution holding the most solute it can at that temperature; extra solute stays undissolved.Ch 5 · Exploring Mixtures and their Separationscientific lawनियमA short statement or equation summing up something nature does every time; it tells what happens, not why.Ch 1 · Exploration: Entering the World of Secondary Sciencescientific principleA general idea with a very wide reach, used to reason about many different situations, such as Archimedes' principle.Ch 1 · Exploration: Entering the World of Secondary Sciencescientific theoryसिद्धांतA well-tested explanation of why certain patterns occur, supported by a large body of evidence and open to improvement.Ch 1 · Exploration: Entering the World of Secondary Sciencesclerenchymaस्क्लेरेन्काइमाA simple tissue of mostly dead cells with thick, lignified walls, giving rigid support and hardness.Ch 3 · Tissues in ActionshellकोशOne of the fixed-energy paths (K, L, M, N…) in which electrons move around the nucleus in Bohr’s model.Ch 8 · Journey Inside the AtomSI unitSI मात्रकA unit of the International System of Units, the agreed worldwide system built on seven base units such as the metre, kilogram and second.Ch 1 · Exploration: Entering the World of Secondary Sciencesimple machineसरल मशीनA device such as a pulley, ramp or lever that changes the size or direction of a force to make a task easier.Ch 7 · Work, Energy, and Simple MachinesslopeढालThe steepness of a line on a graph: change in the y-quantity ÷ change in the x-quantity.Ch 4 · Describing Motion Around Ussolar constantसौर स्थिरांकThe power of sunlight on one square metre facing the Sun, just outside the atmosphere: about 1.4 kW/m².Ch 13 · Earth as a System: Energy, Matter, and LifesolubilityविलेयताThe largest mass of a solute that dissolves in 100 g of a solvent at a stated temperature.Ch 5 · Exploring Mixtures and their SeparationsolutionविलयनA homogeneous mixture of a solute (the substance that dissolves) and a solvent (the substance it dissolves in).Ch 5 · Exploring Mixtures and their SeparationspeciesजातिA group of similar organisms that can interbreed and produce fertile offspring.Ch 12 · Patterns in Life: Diversity and ClassificationsporeबीजाणुA tiny, usually single-celled reproductive body, spread by air or water, that grows into a new organism.Ch 11 · Reproduction: How Life Continuessublimationऊर्ध्वपातनA solid turning straight into vapour on heating, without melting first. The reverse change is called deposition.Ch 5 · Exploring Mixtures and their SeparationsuspensionनिलंबनA heterogeneous mixture whose undissolved particles are big enough to see and settle when left standing.Ch 5 · Exploring Mixtures and their SeparationT
tangentस्पर्श रेखाA straight line that touches a circle at exactly one point.Ch 4 · Describing Motion Around UstendonकंडराA tough cord of connective tissue that joins a muscle to a bone.Ch 3 · Tissues in ActiontensionतनावThe pulling force that a stretched string, rope or chain exerts on the objects tied to its ends.Ch 6 · How Forces Affect Motiontime periodआवर्तकालThe time for one complete oscillation, T = 1/ν; SI unit second.Ch 10 · Sound Waves: Characteristics and ApplicationstissueऊतकA group of similar cells that work together to carry out a particular function.Ch 3 · Tissues in Actiontotipotencyपूर्णशक्तताThe ability of a single cell to divide and differentiate into a complete new organism.Ch 3 · Tissues in Actiontroposphereक्षोभमंडलThe lowest layer of the atmosphere, about 12 km thick on average, where almost all weather happens.Ch 13 · Earth as a System: Energy, Matter, and LifeTyndall effectटिंडल प्रभावThe scattering of a light beam by particles in a colloid or suspension, which makes the path of the beam visible.Ch 5 · Exploring Mixtures and their SeparationU
ultrasonic waveपराश्रव्य तरंगSound of frequency above 20 kHz, too high for humans to hear. Sound below 20 Hz is infrasonic.Ch 10 · Sound Waves: Characteristics and Applicationsuniform circular motionएकसमान वृत्तीय गतिMotion round a circle at constant speed; the velocity keeps changing direction.Ch 4 · Describing Motion Around Usuniform motionएकसमान गतिStraight-line motion with equal distances in equal time intervals, so at constant speed.Ch 4 · Describing Motion Around UsV
vacuoleरसधानीA membrane sac of cell sap; large and central in plant cells, where it keeps the cell firm.Ch 2 · Cell: The Building Block of Lifevalence electronसंयोजकता इलेक्ट्रॉनAn electron in the outermost occupied shell of an atom.Ch 8 · Journey Inside the AtomvalencyसंयोजकताThe combining capacity of an element: the number of electrons its atom loses, gains or shares to complete its outermost shell.Ch 8 · Journey Inside the AtomvalencyसंयोजकताThe combining capacity of an atom or ion: the number of electrons it shares, or the size of its charge.Ch 9 · Atomic Foundations of Mattervascular tissueसंवहन ऊतकPlant tissue that carries water and minerals (xylem) and food (phloem).Ch 12 · Patterns in Life: Diversity and Classificationvegetative propagationकायिक प्रवर्धनGrowing a new plant from a root, stem or leaf of a parent plant, without seeds.Ch 11 · Reproduction: How Life ContinuesvibrationकंपनA rapid, repeated to-and-fro motion of an object about its resting position.Ch 10 · Sound Waves: Characteristics and ApplicationsW
wattवाटThe SI unit of power: one joule per second.Ch 7 · Work, Energy, and Simple Machineswavelengthतरंगदैर्ध्यThe distance between two neighbouring crests (or troughs) of a wave, written λ; SI unit metre.Ch 10 · Sound Waves: Characteristics and ApplicationsweightभारThe pull of gravity that the Earth exerts on an object, equal to mg.Ch 6 · How Forces Affect Motionworkकार्यDone by a force when the object it acts on moves along the force; for a constant force, W = F × s.Ch 7 · Work, Energy, and Simple Machineswork-energy theoremकार्य-ऊर्जा प्रमेयThe work done on an object equals the change in its energy.Ch 7 · Work, Energy, and Simple MachinesX
xylemजाइलमA complex tissue that carries water and minerals up from the roots and gives strength; most of its cells are dead.Ch 3 · Tissues in ActionZ
zygoteयुग्मनजThe single cell formed at fertilisation, which divides to form an embryo.Ch 11 · Reproduction: How Life Continuesncert.ai is an independent learning companion aligned to the NCERT curriculum. It is not affiliated with or endorsed by NCERT.