133 Science Words That Start With I (Grade & Category List)

Looking to expand your scientific vocabulary? This post features 133 science words that start with I, perfect for students, educators, and curious minds. Explore a range of terms from biology, chemistry, physics, and more—all beginning with the letter I.

Dive in and boost your understanding of key science concepts today!

Biology Science Words That Start With I

Grade Level	Word	Definition
Elementary	Insect	A small animal with six legs and usually wings, like ants or bees.
Elementary	Immune	Protected from disease; related to the body’s defense system.
Elementary	Incisor	A type of tooth used for cutting food, found at the front of the mouth.
Middle	Intestine	The long tube in the body that digests food and absorbs nutrients.
Middle	Inhale	To breathe in air.
Middle	Inheritance	Passing of traits from parents to offspring through genes.
Middle	Instinct	A natural, automatic behavior found in animals and humans.
Middle	Interdependence	When living things rely on each other to survive.
Middle	Immunity	The ability of the body to resist disease.
Middle	Incubation	The process of keeping eggs warm until they hatch.
High	Insulin	A hormone that helps control blood sugar levels.
High	Inhibitor	A substance that slows down or stops a chemical reaction or process.
High	Invertebrate	An animal without a backbone, like insects or jellyfish.
High	Inflorescence	The arrangement of flowers on a plant.
High	Interphase	The cell cycle stage when a cell grows and prepares for division.
High	Intron	A segment of DNA or RNA that does not code for proteins.
High	Isoenzyme	Different forms of an enzyme that perform the same function.
High	Imprinting	A rapid learning process in some animals, usually soon after birth.
High	Integumentary	Relating to the skin and its associated structures.
High	Ion Channel	A protein in cell membranes that helps ions pass in and out of cells.
College	Isotonic	Having equal concentration of solutes inside and outside a cell.
College	Isoelectric	The pH at which a molecule carries no electrical charge.
College	Induced Pluripotent	Stem cells created from adult cells that can develop into many types of cells.
College	Immunoglobulin	Proteins (antibodies) in the blood that help fight infection.
College	Interleukin	A type of protein important in cell signaling in the immune system.
College	Isomerase	An enzyme that rearranges molecules within a compound.

Chemistry Science I Words

Grade Level	Word	Definition
Elementary	Ice	Frozen water, a solid form of H2O.
Elementary	Ink	A colored liquid used for writing or printing.
Middle	Ion	An atom or molecule with an electrical charge.
Middle	Indicator	A substance that shows changes in pH or presence of chemicals.
Middle	Iron	A metallic element (Fe), important for blood and many chemical processes.
Middle	Isotope	Atoms of the same element with different numbers of neutrons.
Middle	Impurity	An unwanted substance in a material.
High	Ionic Bond	A chemical bond formed by the transfer of electrons.
High	Intermolecular	Relating to forces or actions between molecules.
High	Ionization	The process of gaining or losing electrons to form ions.
High	Isomer	Molecules with the same formula but different arrangements of atoms.
High	Iridium	A rare, dense metallic element (Ir).
High	Inert Gas	A gas that does not react easily with other substances (like neon or argon).
High	Isopropanol	A chemical compound also known as rubbing alcohol.
High	Immiscible	Liquids that do not mix, like oil and water.
College	Intercalation	Insertion of molecules between layers in a compound (common in chemistry and biology).
College	Isoelectric Point	The pH at which a molecule has no net electric charge.
College	Intramolecular	Within a single molecule.
College	Inhibition	Slowing or stopping a chemical reaction.
College	Isothermal	At a constant temperature.
College	Iodometric	Related to chemical analysis using iodine.
College	Imidazole	A chemical compound found in many important biological molecules.

| Related: 77 Science Words That Start With Z – Vocabulary by Category

Physics Science Words That Start With I

Grade Level	Word	Definition
Elementary	Incline	A slanted surface, like a ramp.
Elementary	Invisible	Something that cannot be seen.
Middle	Inertia	The resistance of an object to a change in motion.
Middle	Impulse	Change in momentum caused by a force acting over time.
Middle	Image	A likeness or reproduction of an object, like in a mirror.
Middle	Insulation	Material that slows the transfer of heat, electricity, or sound.
High	Induction	Generating electric current using a magnetic field.
High	Intensity	The strength or amount of something, like light or sound.
High	Interference	When two waves overlap and combine to form a new wave pattern.
High	Incandescence	Light produced by an object that is hot.
High	Isobaric	Happening at constant pressure.
High	Isochronous	Occurring at equal time intervals.
High	Inelastic	Describes collisions where kinetic energy is not conserved.
High	Inverse Square Law	A law stating that a quantity decreases with the square of the distance.
High	Isotropy	The property of being the same in all directions.
College	Ionization Energy	The energy needed to remove an electron from an atom.
College	Ising Model	A mathematical model for ferromagnetism in physics.
College	Interferometer	An instrument that measures the interference of waves.
College	Infrasonic	Sound waves with frequencies below the range of human hearing.
College	Isoenergetic	Having the same energy.
College	Irreversible	A process that cannot go backward or be undone.

Earth Science Terms That Start With I

Grade Level	Word	Definition
Elementary	Island	A piece of land completely surrounded by water.
Elementary	Iceberg	A large floating piece of ice that has broken off from a glacier.
Middle	Igneous	Type of rock formed from cooled molten lava or magma.
Middle	Ice Age	A period of time when large parts of Earth were covered with ice.
Middle	Ice Sheet	A huge layer of glacier ice covering land for a long period.
High	Isobar	A line on a map connecting points of equal atmospheric pressure.
High	Insolation	The amount of solar radiation reaching a given area.
High	Isotherm	A line on a map connecting points with the same temperature.
High	Intrusion	Molten rock that pushes into or between other rocks below the surface.
High	Intertidal	The coastal area that is above water at low tide and underwater at high tide.
High	Infiltration	The process of water soaking into the ground.
College	Isostasy	The balance of Earth’s crust floating on the mantle.
College	Intermontane	Situated between mountains.
College	Impact Crater	A circular depression caused by a meteorite or asteroid strike.
College	Isopach	A line on a map connecting points of equal thickness in a rock layer.
College	Interglacial	A warmer period between ice ages.

| Related: 230 Science Words That Start With Y: Complete A-Z Guide

General Science I Words

Grade Level	Word	Definition
Elementary	Investigation	The process of looking into or studying something carefully.
Elementary	Idea	A thought or suggestion for a possible solution or explanation.
Elementary	Information	Facts or knowledge shared or learned.
Elementary	Item	An individual object or thing.
Middle	Interpret	To explain the meaning of something.
Middle	Identify	To recognize and name something.
Middle	Infer	To draw a conclusion based on evidence and reasoning.
Middle	Illustrate	To explain or make something clear using examples or pictures.
Middle	Input	Data or information that is entered into a system.
Middle	Inquiry	A process of asking questions to seek information or knowledge.
High	Innovation	A new method, idea, or product.
High	Independent Variable	The factor in an experiment that is changed by the scientist.
High	Inconsistency	A situation where two or more things do not agree or match.
High	Iterate	To repeat a process to get closer to a desired result.
College	Interdisciplinary	Combining or involving two or more academic subjects or fields.
College	Integrative	Bringing together different ideas or information.
College	Inference	A conclusion drawn from evidence and reasoning.
College	Instrumentation	The use of tools or devices for scientific measurement or control.
College	Intellectual Property	Creations of the mind, such as inventions or artistic works, that are legally protected.
College	Intuition	Understanding something immediately, without reasoning.

Technology & Engineering Words That Start With I

Grade Level	Word	Definition
Elementary	Internet	A global network connecting millions of computers.
Elementary	Input Device	A hardware device used to enter data into a computer, like a keyboard.
Middle	Interface	A shared boundary where two systems or devices meet and interact.
Middle	Infrared	Light that has a longer wavelength than visible red light; used in remotes and sensors.
Middle	Iteration	Repeating a process to improve a product or design.
High	Integrated Circuit	A tiny electronic circuit used in computers and other devices.
High	Innovation	The introduction of something new, such as a device or method.
High	Industrial	Related to factories or large-scale production.
High	Interconnection	Linking different systems, devices, or networks together.
College	Instrumentation	Devices used to measure, monitor, and control engineering systems.
College	Implementation	Putting a plan, system, or device into action.
College	Interoperability	The ability of systems or devices to work together.
College	Infrastructure	The basic physical systems needed for operation, like roads or internet.
College	Integration	Combining parts into a whole system.
College	Incremental	Something done step-by-step, in small amounts.
College	Instrumentation Amplifier	An electronic device that increases the strength of electrical signals for measurement.

Conclusion

Exploring these science words that start with I can enhance your vocabulary and deepen your understanding of key concepts across many scientific fields.