Compound (linguistics)

In linguistics, a compound is a lexeme (less precisely, a word or sign) that consists of more than one stem. Compounding, composition or nominal composition is the process of word formation that creates compound lexemes. Compounding occurs when two or more words or signs are joined to make a longer word or sign. Consequently, a compound is a unit composed of more than one stem, forming words or signs. If the joining of the words or signs is orthographically represented with a hyphen, the result is a hyphenated compound (e.g., must-have, hunter-gatherer). If they are joined without an intervening space, it is a closed compound or solid compound (e.g., footpath, blackbird). If they are joined with a space (e.g. school bus, cell phone, high school, lowest common denominator), then the result – at least in English – is an open compound.

The meaning of the compound may be similar to or different from the meaning of its components in isolation. The component stems of a compound may be of the same part of speech—as in the case of the English word footpath, composed of the two nouns foot and path—or they may belong to different parts of speech, as in the case of the English word blackbird, composed of the adjective black and the noun bird. With very few exceptions, English compound words are stressed on their first component stem.

Some languages easily form compounds from what in other languages would be a multi-word expression. This can result in unusually long words, a phenomenon known in German (which is one such language) as Bandwurmwörter ("tapeworm words").

Compounding extends to Sign languages as well, where compounds are also created by combining two or more sign stems.

So-called "classical compounds" are compounds derived from classical Latin or ancient Greek roots.

In many languages, including English, Spanish, Latin and German, all numbers greater than twenty that have more than one non-zero digit are written and spoken as compounds.