Listed below is a collection of some of the most important science vocabulary words used in our class. This page is updated periodically, so be sure to refresh your browser every now and then. If you don’t see a word you are looking for, try visiting Merriam-Webster’s Learner’s Dictionary, a dictionary for younger science students.

ABCD | EFG | HIJK | LMNOP | QRS | TUV | WXY&Z | Root Words | 123s


  • LEAF: usually a green, flattened structure attached to a stem and functioning as a place where photosynthesis and transpiration occurs in most plants.
  • LITHOSPHERE: the rigid outer part of the earth, consisting of the crust and upper mantle.
  • LIQUID: a state of matter in which the particles (e.g., atoms and/or molecules) do not occupy fixed positions and can migrate to other positions in the substance. In the liquid state, the particles (atoms and/or molecules) conform to the shape of a container in which it is held. Although this is also a good definition for the gas (or gaseous) state of matter, in the liquid state the particles (atoms and/or molecules) acquire a defined surface in the presence of gravity. Gases do not typically acquire such defined surfaces in the presence of gravity.


  • MASS: a measure of how much matter (or how many atoms) is in an object or sample combined with the density of those atoms (or how tightly or loosely they are packed together). In our middle science classes we typically use ‘balances’–both electronic and non-electronic–to measure the mass of an object or sample in units such as “grams” or “kilograms.”
  • MATTER: a general term for the substance (or substances) which all physical objects consist.  Matter can also be defined as that which a) takes up space and b) has mass.  In our class, we will often talk about matter as something that contains atoms (and often molecules).
  • MICROBE: Microbe is a term for incredibly tiny organisms that individually are almost always too small to be seen with the unaided eye. (Believe it or not, one species of bacteria has been discovered that is actually about the size of a typed period when using Times New Roman, 12 pt. font!). Microbes include organisms such as bacteria, archaea , fungi, and protists. However, some scientists think that viruses, which are non-living, can also be considered microbes.
  • MICROPYLE: a tiny opening in the ovule of a seed through which a sperm cell can enter. This opening also allows water to enter a mature seed during the process of germination.
  • MINERALS: minerals are naturally occurring (they are not made by humans), inorganic solids (they have never been alive and are not made up from plants or animals), with a definite chemical composition (each one is made of a particular mix of chemical elements), and an ordered atomic arrangement (the chemical elements that make up each mineral are arranged in a particular way – this is why minerals ‘grow’ as crystals). For more information go to The Oxford Museum of Natural History’s website.
  • MIXTURE: two or more substances mixed together.  The mixture may be two or more different types of molecules (e.g., sugar dissolved in water) OR it may be two or more different types of elements (e.g., steel = a mixture of iron (Fe) atoms and carbon (C) atoms). Either way, in a mixture each substance retains its own chemical identity.
  • MOLECULE: two or more atoms bonded together to form a ‘unit.’  The atoms may be of the same type (e.g., O2) or two or more different types (e.g., CO2).
  • MONOCOTYLEDON: a plant whose embryo has one cotyledon.  This word is often abbreviated as “monocot.”


  • NAUPLII (pronounced nor-plee-ee): the name given to the first phase or stage of growth of young crustaceans such as crabs, lobster, and brine shrimp. In this growth stage, the young crustaceans usually have bodies that are not divided into parts (or sections) and possess a single eye.
  • NECTARY: a gland located in flowers (often near the base) that produces a sugary liquid which ‘pollinators’ (e.g., birds and insects) use as food.
  • NEUTRON: a subatomic particle of about the same mass as a proton, but without an electric charge. Neutrons are present in all atomic nuclei except those of ordinary hydrogen (H).
  • NODE: the part of a stem where one or more leaves are attached.


  • OMNIVORE: an animal or person that eats food of both plant and animal origin.
  • ORGANIC COMPOUND: any substance that contains a chain of carbon (C) atoms, but also most likely hydrogen (H) and oxygen (O) atoms. In science class, we will use the word “CHO” to remind ourselves of substances that are organic.
  • ORGAN: a group of tissues (specialized cells) that perform a specific function or group of functions. Examples of animal organs include heart, lungs, brain, eye, and stomach. Examples of plant organs include roots, stems, leaves, flowers, seeds, and fruit.
  • ORGANISM: highly organized, coordinated structures that consist of one or more cells. Even bacteria [singular: bacterium], each of which consists of only a single cell, are considered to be organisms.
  • ORGANELLE: a specialized unit within a cell that has a specific function (or functions). Individual organelles are usually separately enclosed within their own membranes. Contrary to popular opinion, the cytoplasm is not an organelle (the cytoplasm consists of the cytosol–the liquid in which organelles are suspended–and the organelles themselves).
  • ORGAN SYSTEM: A group of organs that work together to carry out a particular function (task, job). An example of an organ system found in humans is the digestive system.
  • OVARY: the enlarged base of the pistil in which the ovules are contained.  It is sometimes called the carpel.
  • OVULE: a structure in seed-producing plants that contains the egg cell.
  • OXYGEN: a chemical element with symbol O and atomic number 8. It is one of the 92 naturally occurring elements on Earth. A single oxygen atom typically contains 8 protons, 8 neutrons, and 8 electrons.


  • PARTICLE: in our science classes, we will often use the word “particle” to refer to an extremely small portion of matter. At some point, however, we will start replacing the word “particle” with more precise words such as “atom” and “molecule.”
  • PATTERN: a natural or accidental arrangement or sequence; a regular and intelligible form or sequence discernible in the way in which something happens or is done.
  • PEDICEL: the stem-like structure just below the receptacle that connects a single flower (or flower bud) to stem or branch of stems leading to other flowers.
  • PERENNIAL PLANT: a plant that lives year after year and usually produces reproductive structures in two or more years.
  • PETAL: a flower part that is usually colored to help attract ‘pollinators’ (e.g., birds and insects).
  • PETIOLE: the stem-like structure just below the base of the leaf that connects a leaf blade to a plant stem.
  • PHOTOSYNTHESIS: a process occurring in plants and plant-like organisms (e.g., some bacteria) in which light energy from the sun is converted into chemical energy and stored in the form of food (e.g., glucose, sugars, starch) OR a process that uses light to put together carbon dioxide (CO2) and water (H2O) to make food (sugars = CHO).  The energy from the sun is used to split apart the water and carbon dioxide molecules.  Pieces of the molecules are rearranged to make a new substance, sugars.
  • PHOTOTROPISM: the response of a shoot or root to light.
  • PHYSICAL: of or related to…the properties of matter and energy and the relationship between them.
  • PISTIL: the female organ of a flower which produces ovules.  It typically consists of three parts: the stigma, the style, and the ovary (or carpel).
  • POLLEN (or POLLEN GRAINS): a structure in seed-producing plants that contains the sperm cell.  Plants often make it in great quantities.
  • POLLINATION: the transfer of pollen from the anther (a special part of the male organ) to the stigma (a special part of the female organ).
  • POOL (in stream or river): a reach of a stream that is characterized by deep, low-velocity water and a smooth surface.’
  • PLANT: a living thing that grows in the ground, usually has leaves or flowers, and needs a source of light (e.g., from the sun), a source of water (e.g., from the rain), and a source of carbon dioxide (from the air) to survive.
  • PLUMULA: same as plumule (see below).
  • PLUMULE: the first ‘bud’ of an embryo.  It is the portion of a young ‘shoot’ above the cotyledons.  Some people like to refer to the plumule as the “future stem and leaves.”
  • PRIMARY CONSUMER: animals that are specially adapted to a diet consisting mainly or exclusively of plant materials.
  • PRODUCER: an organism capable of making their own food. In other words, they produce complex organic compounds (e.g., glucose) from simple inorganic molecules (e.g., CO2 and H2O) through the process of photosynthesis (using light energy) or chemosynthesis (using chemical energy).
  • PROTON: a stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron.
  • PURE SUBSTANCE: a pure substance consists of only one type of molecule (e.g., pure water) OR only one type of element (pure gold).

ABCD | EFG | HIJK | LMNOP | QRS | TUV | WXY&Z | Root Words | 123s

 Last updated: May 2017

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