130 Important Science Words That Start With I (With Meanings)

Science is filled with fascinating words, and many of them begin with the letter Science Words That Start With I. Knowing these science words starting with I helps students, teachers, and curious learners connect ideas across biology, chemistry, physics, earth science, and technology. This article gives you a full science glossary I words list, with simple meanings and examples that make learning easier. The goal is to provide a clear science dictionary words guide for anyone who wants to understand important scientific terms beginning with Science Words That Start With I.

Biology Science Words

Word	Meaning (Easy English)	Example
Immune system	Body defense against illness	The immune system fights viruses.
Insulin	Hormone that controls blood sugar	Insulin lowers glucose levels.
Invertebrate	Animal without a backbone	Spiders are invertebrates.
Inheritance	Traits passed from parents to children	Brown eyes can be inherited.
Incisor	Front tooth used for cutting	Humans have four incisors.
Ingestion	Taking food into the body	Ingestion starts digestion.
Intestine	Long tube in the digestive system	Food is absorbed in the intestine.
Inhalation	Breathing air into the lungs	Inhalation gives oxygen.
Infection	Harm caused by harmful microbes	A cold is an infection.
Inoculation	Giving vaccine for protection	Inoculation prevents disease.

Biology Science Words

Word	Meaning	Example
Inhibitor	Substance that slows a reaction	Enzyme inhibitors block reactions.
Infestation	Invasion by pests or parasites	Fleas cause infestation in pets.
Influenza	Viral infection of the lungs	Influenza spreads in winter.
Insemination	Process of fertilization	Artificial insemination helps farming.
Instinct	Natural behavior pattern	Birds migrate by instinct.
Integument	Outer covering like skin	The integument protects the body.
Interphase	Stage between cell divisions	DNA replicates in interphase.
Interneuron	Nerve cell connecting other neurons	Interneurons send brain signals.
Isopod	Small crustacean with many legs	Pill bugs are isopods.
Isomerase	Enzyme that changes molecule structure	Isomerase helps metabolism.

Chemistry Science Words

Word	Meaning	Example
Ion	Atom with positive or negative charge	Salt forms sodium ions.
Ionic bond	Attraction between charged atoms	NaCl has an ionic bond.
Isotope	Same element with different mass	Carbon-14 is an isotope.
Isomer	Same formula, different structure	Glucose and fructose are isomers.
Indicator	Shows if a substance is acid or base	Litmus paper is an indicator.
Inorganic	Not made of carbon chains	Water is an inorganic compound.
Intermolecular	Forces between molecules	Water molecules stick together.
Inert gas	Gas that does not react	Helium is an inert gas.
Inhibitor	Slows down chemical reactions	Catalysts sometimes need inhibitors.
Insoluble	Cannot dissolve in water	Sand is insoluble in water.

Chemistry Science Words

Word	Meaning	Example
Ignition	Start of burning reaction	Ignition begins combustion.
Immiscible	Liquids that don’t mix	Oil and water are immiscible.
Interhalogen	Compound of halogens	Iodine chloride is interhalogen.
Intermediate	Temporary product in a reaction	Carbocation is an intermediate.
Initiator	Substance that starts reaction	Light can be an initiator.
Ionization	Process of forming ions	Water ionizes into H⁺ and OH⁻.
Inertial mass	Resistance to acceleration	Measured in kilograms.
Isobar	Atoms with same mass, different number	Argon-40 and Calcium-40 are isobars.
Isothermal	Constant temperature process	Isothermal expansion of gases.
Isotonic	Same concentration on both sides	Saline is isotonic to blood.

Physics Science Words

Word	Meaning (Easy English)	Example
Inertia	Resistance to motion change	A ball keeps rolling due to inertia.
Impulse	Force applied over time	A bat gives impulse to a ball.
Intensity	Strength of light or sound	The intensity of the sound is loud.
Interference	Meeting of two waves	Noise-canceling headphones use interference.
Isotopes	Atoms with different neutron numbers	Uranium isotopes are used in reactors.
Inclined plane	Sloped surface used to lift objects	A ramp is an inclined plane.
Induction	Creating current without contact	Generators work by induction.
Insulator	Material that blocks electricity	Rubber is an insulator.
Isothermal process	Change with constant temperature	Gas expands in an isothermal process.
Irregular motion	Movement without a fixed pattern	A leaf shows irregular motion in the wind.

Physics Science Words

Word	Meaning	Example
Inelastic collision	Collision where energy is lost	A car crash is inelastic.
Isobaric process	Constant pressure change	Heating gas in open air is isobaric.
Isentropic	Constant entropy process	Ideal engines have isentropic steps.
Internal energy	Energy stored inside matter	Molecules hold internal energy.
Ionization energy	Energy to remove an electron	Hydrogen has low ionization energy.
Intermolecular distance	Space between molecules	Solids have small intermolecular distance.
Ideal gas	Gas following gas laws perfectly	Oxygen acts like an ideal gas at low pressure.
Image	Visual reproduction of object	A mirror forms an image.
Isotropy	Same property in all directions	Glass shows isotropy.
Infrared radiation	Heat radiation beyond visible light	Remote controls use infrared radiation.

Earth Science Words

Word	Meaning	Example
Igneous rock	Rock from cooled magma	Granite is an igneous rock.
Ice age	Period with widespread glaciers	Mammoths lived in the ice age.
Infiltration	Water entering soil	Rainwater infiltrates the ground.
Irrigation	Supplying water to crops	Farmers use drip irrigation.
Iron ore	Natural source of iron	Steel is made from iron ore.
Island arc	Chain of volcanic islands	Japan is an island arc.
Isobar (weather)	Line of equal pressure	Weather maps use isobars.
Isotherm	Line of equal temperature	Climate maps show isotherms.
Intertidal zone	Area between high and low tide	Crabs live in the intertidal zone.
Iceberg	Large floating ice piece	Ships avoid icebergs in cold seas.

Earth Science Words

Word	Meaning	Example
Ice sheet	Vast glacier covering land	Antarctica has an ice sheet.
Insolation	Sunlight reaching Earth	Insolation heats the planet.
Intrusive rock	Igneous rock cooled underground	Granite is intrusive rock.
Impact crater	Hole made by meteorite	Meteor Crater in Arizona is an impact crater.
Isopod fossil	Ancient marine crustacean remains	Trilobites are isopod fossils.
Inundation	Flooding of land	Nile floods were called inundations.
Ice cap	Small glacier on mountains	Iceland has ice caps.
Isoclinal fold	Geological fold with parallel limbs	Found in mountain belts.
Island ecosystem	Living systems on islands	Galápagos is an island ecosystem.
Iron core	Center of Earth made of iron	Earth has an iron core.

Technology & Engineering Words

Word	Meaning	Example
Infrared technology	Heat-based sensing system	Thermal cameras use infrared technology.
Interface	Point where two systems connect	Computers use a user interface.
Integrated circuit	Tiny electronic chip	Phones run on integrated circuits.
Innovation	New creative solution	Solar panels are an innovation.
Iteration	Repeated design improvement	Apps improve through iteration.
Input	Data put into a system	Keyboard input gives instructions.
Inverter	Device changing current type	Solar panels use inverters.
Insulation	Material preventing heat loss	Houses use thermal insulation.
Industrialization	Growth of factories and machines	Industrialization changed human life.
Injection molding	Method to shape materials	Plastic toys are made by injection molding.

Technology & Engineering Words

Word	Meaning	Example
Instrumentation	Tools for measurement	Labs use instrumentation systems.
Internet	Global network of computers	The internet spreads scientific information.
Iterative testing	Repeated trial process	Engineers use iterative testing in designs.
Isotropic material	Same properties in all directions	Steel is isotropic.
Intelligent system	Machine that makes decisions	AI is an intelligent system.
Ingress protection	Rating for dust/water safety	Phones have IP68 ingress protection.
Impact strength	Resistance to sudden force	Helmets have high impact strength.
Injection system	Device that injects fluid	Cars use fuel injection systems.
Isolation transformer	Electrical safety device	Labs use isolation transformers.
Information technology	Science of data systems	IT powers modern communication.

General Science Words

Word	Meaning	Example
Inference	Conclusion from evidence	Scientists use inference in research.
Investigation	Process of study or testing	A lab investigation studies bacteria.
Instrument	Tool for measurement	A microscope is a scientific instrument.
Independent variable	Factor changed in experiment	Light is an independent variable in plant growth tests.
Information	Knowledge from data	Computers store scientific information.
Index fossil	Fossil used to date rocks	Trilobites are index fossils.
Inquiry	Asking questions to learn	Scientific inquiry begins with curiosity.
Innovation science	Applying new ideas in science	Vaccines are results of innovation science.
Input energy	Energy supplied to a system	Electricity is input energy in a fan.
Inertia of rest	Object stays still until moved	A rock shows inertia of rest.

Words of General Science

Word	Meaning	Example
Inertia of motion	Object keeps moving unless stopped	A moving car has inertia of motion.
Interdisciplinary	Mixing many sciences together	Climate science is interdisciplinary.
Isomorphic	Having similar form	Crystals can be isomorphic.
Integration	Combining ideas into one system	Integration of physics and math helps research.
Isotherm line	Constant temperature line	Weather maps show isotherm lines.
Industrial chemistry	Chemistry used in industries	Fertilizers come from industrial chemistry.
Isotonic solution	Same pressure as body fluids	Sports drinks are isotonic.
Isometric	Equal dimensions or measurements	Isometric exercises build strength.
Insomnia (medical)	Disorder of sleep studied in science	Insomnia affects brain health.
Inheritance law	Laws of genetics	Mendel explained inheritance laws.

General Science Words

Word	Meaning	Example
Immunology	Study of immune system	Immunology helps vaccine research.
Ichthyology	Study of fish	Ichthyology explains fish biology.
Ichnology	Study of fossil tracks	Dinosaur footprints are ichnology evidence.
Isotherm reaction	Reaction with constant temperature	Some reactions are isotherms.
Interplanetary	Between planets	Interplanetary travel is space science.
Ionosphere	Atmospheric layer with ions	Radio signals reflect in the ionosphere.
Isometry	Equal measurement property	Isometry is used in geometry.
Incubation	Growth under controlled conditions	Eggs hatch after incubation.
Impedance	Opposition to current	Circuits show electrical impedance.
Invertebrate zoology	Study of animals without backbones	Invertebrate zoology covers insects and worms.

Conclusion

Exploring 130 science words that start with I shows how much science connects to life, nature, and technology. These words cover biology, chemistry, physics, earth science, and engineering. From the immune system definition in biology to infrared technology in engineering, these terms give a clear picture of how science shapes our world. Understanding this Science Words That Start With I collection helps students, teachers, and readers gain confidence in learning science. The more familiar you are with these Science Words That Start With I, the more prepared you’ll be for deeper studies and real-world applications.