a word consisting of no fewer than two stems, each having a full lexical meaning, that together form a structural and semantic unit. Compound words are formed by joining two or more autonomous words (content) or the stems of these words into a complex whole according to a certain lexical pattern, as with the Russian words teploprovod (“hot-water pipe,” “steam pipe”), avianosets (“aircraft carrier”) and vertolet (“helicopter”). They may also be formed by nominalization, that is, by contraction and semantic compression of a syntactic construction (a word combination or clause); an example is found in the English “crybaby,” formed from “a baby cries.”

Compound words differ from word combinations or affixal derivatives graphically in that they are written as single words and phonetically in that they have a single strong stress. Morphologically they are distinct in that their parts are sometimes joined by a special connective morpheme, as with the Russian par-o-khod (“steamship”) and the German Nahrung-s-mittel (“means of nourishment”). There are also certain semantic features peculiar to compound words. Compound words can be classified on the basis of the relationship between their component parts. In German, the Scandinavian languages, and many other European languages, compound words are created in speech as readily as are word combinations; they are ad hoc in character and are not always recorded in dictionaries.