In etymology, a root (sometimes named an etymon) is the original form from which a word, or a group of words, has been derived. Sometimes the same root can give rise to branches in different languages: for example, the English word reason, the French word raison and the Italian word ragione are all derived from the Latin root ratio - which also gives English the mathematical word 'ratio'. (The meaning of root is itself derived: it is a figurative development of the root 'root', literally meaning the underground part of a plant which nourishes it and holds it in place.)
"One of those ultimate elements of a language, that cannot be further analysed, and form the base of its vocabulary; a primary word or form from which others are derived" (OED).
- The etymological root of a word is known by many writers as its stem. In itself, this may be etymologically interesting: both root and stem are metaphors, and both are drawn from botany; but they are different parts of the plant.