| A | B |
|---|
| fault | a crack in the Earth's crust, along which crustal movement takes place |
| fermentation | an enzyme-controlled reaction that takes place in the absence of oxygen, such as the conversion of sugar to alcohol by the action of yeast |
| fertilization (botany) | the process of applying nutrients to the soil to stimulate plant growth |
| fertilization (biology) | the union of a sperm and an egg cell to form a zygote |
| fission (biology) | the reproduction of a one-celled organism by splitting into two equal parts |
| fission (physics) | splitting of an atomic nucleus into approximately equal parts, with the release of energy |
| flood plain | the flat region around an old river, which becomes covered with water at times of high runoff |
| food chain | an array of organisms in which each serves as food for the one above |
| fossil | the preserved remains of a long-extinct organism |
| frequency | the number of cycles completed in a unit time in any cyclic phenomenon, such as a vibration |
| front | the boundary between two air masses |
| fusion (physics) | the melting of a solid or a nuclear reaction in which two small nuclei combine to form a larger one, accompanied by the release of energy |
| fusion (biology) | the union of isogametes of one-celled organisms |
