Nominal compound

In linguistics, a compound is a lexeme (less precisely, a word) that consists of more than one stem. Compounding, composition or nominal composition is the process of word formation that creates compound lexemes. That is, in familiar terms, compounding occurs when two or more words are joined to make one longer word. The meaning of the compound may be similar to or different from the meanings 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.

The process occurs readily in other Germanic languages for different reasons. Words can be concatenated both to mean the same as the sum of two words (e.g. Pressekonferenz — German for press conference) or where an adjective and noun are compounded (e.g. hvidvinsglas — Danish for white wine glass).

The addition of affix morphemes to words (such as suffixes or prefixes, as in employ → employment) should not be confused with nominal composition, as this is actually morphological derivation.

Compound formation rules vary widely across language types.

In a synthetic language, the relationship between the elements of a compound may be marked with a case or other morpheme. For example, the German compound Kapitänspatent consists of the lexemes Kapitän (sea captain) and Patent (license) joined by an -s- (originally a genitive case suffix); and similarly, the Latin lexeme paterfamilias contains the archaic genitive form familias of the lexeme familia (family). Conversely, in the Hebrew language compound, the word בֵּית סֵפֶר bet sefer (school), it is the head that is modified: the compound literally means "house-of book", with בַּיִת bayit (house) having entered the construct state to become בֵּית bet (house-of). This latter pattern is common throughout the Semitic languages, though in some it is combined with an explicit genitive case, so that both parts of the compound are marked (e.g. Arabic عبد الله ʕabdu ʔal-lāhi "servant-of-God").

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