Morpheme

In morpheme-based morphology, a morpheme is the smallest linguistic unit that has semantic meaning. In spoken language, morphemes are composed of phonemes (the smallest linguistically distinctive units of sound), and in written language morphemes are composed of graphemes (the smallest units of written language).

The concept morpheme differs from the concept word, as many morphemes cannot stand as words on their own. A morpheme is free if it can stand alone, or bound if it is used exclusively alongside a free morpheme. Its actual phonetic representation is the morph, with the morphs representing the same morpheme being grouped as its allomorphs.

The word "unbreakable" has three morphemes: "un-" (meaning not x), a bound morpheme; "-break-", a free morpheme; and "-able", a bound morpheme. "un-" is also a prefix, "-able" is a suffix. Both are affixes.
 * English example:

The morpheme plural-s has the morph "-s",, in cats , but "-es", , in dishes , and even the voiced "-s", , in dogs. These are the allomorphs of "-s". It might even change entirely into -ren in children.

Types of morphemes

 * Free morphemes like town, and dog can appear with other lexemes (as in town hall or dog house) or they can stand alone, i.e. "free".
 * Bound morphemes (or affixes) like "un-" appear only  together with other morphemes to form a lexeme. Bound morphemes in general tend to be prefixes and suffixes.  Unproductive, non-affix morphemes that exist only in bound form are known as "cranberry" morphemes, from the "cran" in that very word.
 * Derivational morphemes can be added to a word to create (derive) another word: the addition of "-ness" to "happy," for example, to give "happiness." They carry semantic information.
 * Inflectional morphemes modify a word's tense, number, aspect, and so on (as in the "dog" morpheme if written with the plural marker morpheme "-s" becomes "dogs"). They carry grammatical information.
 * Allomorphs are variants of a morpheme, e.g. the plural marker in English is sometimes realized as, or ].

Other variants

 * Null morpheme
 * Root morpheme
 * Word stem

Morphological analysis
In natural language processing for Japanese, Chinese and other languages, morphological analysis is the process of segmenting a given sentence into a row of morphemes. It is closely related to Part-of-speech tagging, but word segmentation is required for these languages because word boundaries are not indicated by blank spaces. Famous Japanese morphological analysts include Juman and ChaSen.