A monosyllabic language is a language in which words predominantly consist of a single syllable. An example of a monosyllabic language would be Old Chinese[1] or Vietnamese, Burmese or Sumerian
Monosyllabism is the name for the property of single-syllable word form. The natural complement of monosyllabism is polysyllabism.
Whether a language is monosyllabic or not sometimes depends on the definition of "word", which is far from being a settled matter among linguists.[2] For example, Modern Chinese (Mandarin) is "monosyllabic" if each written Chinese character is considered a word; which is justified by observing that most characters have proper meaning(s) (even if very generic and ambiguous).[3] However, most entries in a Chinese dictionary are compounds of two or more characters; if those entries are taken as the "words", then Mandarin is not truly monosyllabic, only its morphemes are.[1][4]
an overwhelmingly high percentage of Chinese segmental morphemes (bound or free) consist of a single syllable; no more than perhaps five percent are longer than one syllable, and only a small handful are shorter. In this sense — in the sense of the favored canonical shape of morphemes — Chinese is indeed monosyllabic