Definition · Plain-language
Morpheme
A morpheme is the smallest unit of language that carries meaning — for example the word cat, or the plural suffix -s in cats.
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The smallest unit of meaning
A morpheme is the smallest part of a word that still carries meaning or grammatical function. It cannot be divided further without losing that meaning. The word unhappiness has three morphemes: un- (not), happy (the root meaning) and -ness (a state of being). Each contributes something; removing any changes the meaning. Morphology, the study of word structure, analyses how morphemes combine to build words. Counting morphemes is different from counting syllables: cats has two morphemes but one syllable, while crocodile has one morpheme but three syllables — meaning and sound are measured separately.
Free and bound morphemes
Morphemes divide into two basic types. A free morpheme can stand alone as a word: book, happy, run, and the. A bound morpheme cannot stand alone and must attach to another morpheme — these include all affixes, such as the prefix un-, the suffix -ness and the plural -s, as well as bound roots like the ject in reject. Bound morphemes split further into derivational ones, which create new words or change word class (-ness, -ly), and inflectional ones, which mark grammar such as tense or number (-ed, -s). Every word is built from at least one free or bound morpheme.
Morpheme, root and affix
Morpheme is the umbrella concept; root and affix are kinds of morphemes. A root is the central morpheme carrying core meaning; a prefix and a suffix are bound morphemes (affixes) attached to it. So in rewritable, re- (prefix) and -able (suffix) are bound morphemes added to the free morpheme write. One spoken or written form can also represent different morphemes — the -s in cats marks plural, but the -s in runs marks third-person singular — and one morpheme can have different forms, as the plural takes -s, -es or an internal change. Distinguishing the abstract morpheme from its surface forms is central to morphology.
Key facts
At a glance
- Definition: the smallest meaningful unit of language
- Study of: morphology — the structure of words
- Free morpheme: can stand alone — book, run, happy
- Bound morpheme: must attach to another — un-, -ness, -s
- Not the same as: a syllable (a unit of sound, not meaning)
- Example: cats = cat + -s (two morphemes)
Common misconceptions
What people often get wrong
Often heard: A morpheme is the same as a syllable.
Actually: They measure different things. A morpheme is the smallest unit of meaning; a syllable is a unit of sound. Cats has one syllable but two morphemes; crocodile has three syllables but one morpheme.
Often heard: Every morpheme can be used as a word on its own.
Actually: Only free morphemes can stand alone (book, run). Bound morphemes such as un-, -ness and -s carry meaning but must attach to another morpheme to be used.
Often heard: A morpheme and a root word are the same thing.
Actually: A root is one kind of morpheme — the meaning-bearing core. Affixes such as prefixes and suffixes are also morphemes. Morpheme is the broader category that includes both roots and affixes.
Going deeper
