atom: The basic unit of a chemical element. Atoms are made up of a dense nucleus that contains positively charged protons and uncharged neutrons. The nucleus is orbited by a cloud of negatively charged electrons.
cell: The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.
climate: The weather conditions that typically exist in one area, in general, or over a long period.
climate change: Long-term, significant change in the climate of Earth. It can happen naturally or in response to human activities, including the burning of fossil fuels and clearing of forests.
electricity: A flow of charge, usually from the movement of negatively charged particles, called electrons.
electron: A negatively charged particle, usually found orbiting the outer regions of an atom; also, the carrier of electricity within solids.
excite: (in chemistry and physics) To transfer energy to one or more outer electrons in an atom. They remain in this higher energy state until they shed the extra energy through the emission of some type of radiation, such as light.
fossil: Any preserved remains or traces of ancient life. There are many different types of fossils: The bones and other body parts of dinosaurs are called “body fossils.” Things like footprints are called “trace fossils.” Even specimens of dinosaur poop are fossils. The process of forming fossils is called fossilization.
fossil fuel: Any fuel — such as coal, petroleum (crude oil) or natural gas — that has developed within the Earth over millions of years from the decayed remains of bacteria, plants or animals.
fuel: Any material that will release energy during a controlled chemical or nuclear reaction. Fossil fuels (coal, natural gas and petroleum) are a common type that liberate their energy through chemical reactions that take place when heated (usually to the point of burning).
green: (in chemistry and environmental science) An adjective to describe products and processes that will pose little or no harm to living things or the environment.
greenhouse: A light-filled structure, often with windows serving as walls and ceiling materials, in which plants are grown. It provides a controlled environment in which set amounts of water, humidity and nutrients can be applied — and pests can be prevented entry.
greenhouse gas: A gas that contributes to the greenhouse effect by absorbing heat. Carbon dioxide is one example of a greenhouse gas.
particle: A minute amount of something.
photon: A particle representing the smallest possible amount of light or other type of electromagnetic radiation.
photovoltaic: An adjective that describes the ability of certain technologies to convert sunlight into electricity.
power plant: An industrial facility for generating electricity.
renewable: An adjective for resources that can be endlessly replaced (such as water, green plants, sunlight and wind). This is in contrast to non-renewable resources, for which there is a finite supply — one that can essentially be used up. These include petroleum (and other fossil fuels) or relatively rare elements and minerals.
renewable energy: Energy from a source that is not depleted by use, such as hydropower (water), wind power or solar power.
solar: Having to do with the sun or the radiation it emits. It comes from sol, Latin for sun.
solar cell: A device that converts solar energy to electricity.
solar energy: The energy in sunlight that can be captured as heat or converted into heat or electrical energy. Some people refer to wind power as a form of solar energy. The reason: Winds are driven by the variations in temperatures and the density of the air, both of which are affected by the solar heating of the air, ground and surface waters.
sun: The star at the center of Earth’s solar system. It is about 27,000 light-years from the center of the Milky Way galaxy. Also a term for any sunlike star.
waste: Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.