morphophonemics, in linguistics, study of the relationship between morphology (q.v.) and phonology (q.v.). Morphophonemics involves an investigation of the phonological variations within morphemes, usually marking different grammatical functions; e.g., the vowel changes in “sleep” and “slept,” “bind” and “bound,” “vain” and “vanity,” and the consonant alternations in “knife” and “knives,” “loaf” and “loaves.”