Compound noun

A compound is a word composed of more than one free morpheme. The English language, like many others, uses compounds frequently. English compounds may be classified in several ways, such as the word classes or the semantic relationship of their components.

Most English compound nouns are noun phrases (i.e. nominal phrases) that include a noun modified by adjectives or noun adjuncts. Due to the English tendency towards conversion, the two classes are not always easily distinguished. Most English compound nouns that consist of more than two words can be constructed recursively by combining two words at a time. Combining "science" and "fiction", and then combining the resulting compound with "writer", for example, can construct the compound "science fiction writer". Some compounds, such as salt and pepper or mother-of-pearl, cannot be constructed in this way,

Since English is a mostly analytic language, unlike most other Germanic languages, it creates compounds by concatenating words without case markers. As in other Germanic languages, the compounds may be arbitrarily long. However, this is obscured by the fact that the written representation of long compounds always contains spaces. Short compounds may be written in three different ways, which do not correspond to different pronunciations, however:

Usage in the US and in the UK differs and often depends on the individual choice of the writer rather than on a hard-and-fast rule; therefore, open, hyphenated, and closed forms may be encountered for the same compound noun, such as the triplets container ship/container-ship/containership and particle board/particle-board/particleboard.

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