The root in language is either a base word, or a part of a word to which affixes are added. Or, it is the part left after affixes have been taken away. Technically, it is the smallest unit which carries meaning: it cannot be reduced into smaller units. It is the same as a free-standing morpheme.
Examples: in each case in bold
- McArthur, Tom 1992. The Oxford companion to the English language. Oxford Unniversity Press, 876.