A reader asks about the terms prefix, root, and suffix, and wonders how to distinguish them in a word.
At the most basic level, words are made up of units of meaning called morphemes. A morpheme may be a recognizable word like tree, run, or button that cannot be broken down into smaller meaningful parts.
A morpheme can represent meaning without being a word. For example, the prefix un- expresses the idea of negation. The suffix -ness, used to turn adjectives into abstract nouns, is a morpheme. The root struct, seen in structure and construct, is a morpheme that embodies the meaning of “to build,” but it cannot stand alone as an English word.
A root is a word’s basic part and carries its fundamental meaning. In the word sadness, for example, the root is sad. Sometimes two roots combine to make one word, as in telephone, a combination of the morpheme tele, which relates to distance, and the morpheme phone, which relates to sound.
Prefixes and suffixes belong to a set of morphemes called affixes. An affix is an element added to the base form or stem of a word to modify its meaning.
Standard English makes use of two types of affix: prefixes and suffixes. A prefix is added at the beginning of a word. For example, the prefix re- is added to a root or a word to denote the idea of doing it again: return, renew, reconstruct.
A suffix is added at the end of a word.
Suffixes are of two kinds, derivational and inflectional. A derivational suffix changes the underlying meaning of the word; an inflectional suffix changes the tense of a verb or the number of a noun, or performs some other grammatical purpose.
Some common derivational suffixes are, -er, -al, -ful, and -ize. The suffix -er added to a verb creates a person or object that performs the action of the verb: teach/teacher, walk/walker, kill/killer, compute/computer; -al and -ful change nouns into adjectives: accident/accidental, forget/forgetful; -ize changes a noun into a verb: terror/terrorize.
Common inflectional suffixes are endings such as, –ed, -ly, -‘s, -s, -er, -ed, -es, -est, and -ing.
Derivational endings are added to a root. For example, the word reconstruction is made up of the root struct, two prefixes, re- and con-, and a suffix, tion. (Because struct ends in t and tion begins with t, one of the ts had to go.)
Inflectional endings are added to a stem, which is the entire word that the ending is being added to. In the words reconstructed and reconstructing, for example, the stem is reconstruct-.