Definition
A "morpheme" is a short segment of language that meets three basic criteria:
1. It is a word or a part of a word that has meaning.
2. It cannot be divided into smaller meaningful segments without changing its meaning or leaving a meaningless remainder.
3. It has relatively the same stable meaning in different verbal environments.
Free and Bound Morphemes
There are two types of morphemes-free morphemes and bound morphemes. "Free morphemes" can stand alone with a specific meaning, for example, eat, date, weak. "Bound morphemes" cannot stand alone with meaning. Morphemes are comprised of two separate classes called (a) bases (or roots) and (b) affixes.
A "base," or "root" is a morpheme in a word that gives the word its principle meaning. An example of a "free base" morpheme is woman in the word womanly. An example of a "bound base" morpheme is -sent in the word dissent.
Affixes
An "affix" is a bound morpheme that occurs before or after a base. An affix that comes before a base is called a "prefix." Some examples of prefixes are ante-, pre-, un-, and dis-, as in the following words:
antedate
prehistoric
unhealthy
disregard
An affix that comes after a base is called a "suffix." Some examples of suffixes are -ly, -er, -ism, and -ness, as in the following words:
happily
gardener
capitalism
kindness
Derivational Affixes
An affix can be either derivational or inflectional. "Derivational affixes" serve to alter the meaning of a word by building on a base. In the examples of words with prefixes and suffixes above, the addition of the prefix un- to healthy alters the meaning of healthy. The resulting word means "not healthy." The addition of the suffix -er to garden changes the meaning of garden, which is a place where plants, flowers, etc., grow, to a word that refers to 'a person who tends a garden.' It should be noted that all prefixes in English are derivational. However, suffixes may be either derivational or inflectional.
Inflectional Affixes
There are a large number of derivational affixes in English. In contrast, there are only eight "inflectional affixes" in English, and these are all suffixes. English has the following inflectional suffixes, which serve a variety of grammatical functions when added to specific types of words. These grammatical functions are shown to the right of each suffix.
-s noun plural
-'s noun possessive
-s verb present tense third person singular
-ing verb present participle/gerund
-ed verb simple past tense
-en verb past perfect participle
-er adjective comparative
-est adjective superlative