Compound nouns are formed by combining two (or more) words. The two words have different meanings separately. But together they have a new meaning.
1. What is a Compound Noun?
Most English compound nouns are noun phrases (= nominal phrases) that include a noun modified by adjectives or attributive nouns. 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.
2. Types of Compound Nouns
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:
- The “solid” or “closed” forms in which two usually moderately short words appear together as one. Solid compounds most likely consist of short (monosyllabic) units that often have been established in the language for a long time. Examples are housewife, lawsuit, wallpaper, basketball, etc.
- The hyphenated form in which two or more words are connected by a hyphen. Compounds that contain affixes, such as house-build(er) and single-mind(ed)(ness), as well as adjective-adjective compounds and verb-verb compounds, such as blue-green and freeze-dried, are often hyphenated. Compounds that contain articles, prepositions or conjunctions, such as rent-a-cop, mother-of-pearl and salt-and-pepper, are also often hyphenated.
- The open or spaced form consisting of newer combinations of usually longer words, such as distance learning, player piano, lawn tennis, etc.
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.
3. Plural Forms of Compound Nouns
In general we make the plural of a compound noun by adding -s to the “base word” (the most “significant” word). Look at these examples:
- a school teacher – three school teachers
- one assistant headmaster – five assistant headmasters
- the sergeant major – some sergeants major
- a mother-in-law – two mothers-in-law
- an assistant secretary of state – three assistant secretaries of state
- my toothbrush – our toothbrushes
- a woman-doctor – four women-doctors
- a doctor of philosophy – two doctors of philosophy
- a passerby, a passer-by – two passersby, two passers-by
Note that there is some variation with words like spoonful or truckful. The old style was to say spoonsful or trucksful for the plural. Today it is more usual to say spoonfuls or truckfuls. Both the old style (spoonsful) and the new style (spoonfuls) are normally acceptable, but you should be consistent in your choice.