The phonemic inventory (overall pattern) of a language must account for every contrast occurring in any idiolect. Utterances occur in the phonemes of an idiolect, and phonemes are therefore the ultimate units of lexical items. But a three-stratum, twenty-seven level model for linguistic analysis indicates structural units—the morphophones—between phoneme and morpheme. Morphophones are seen as the basic units of the morphemes, and are themselves composed of dialectally different phonemic variants, which are non-contrasting in the same lexical items. Further, there are systematic alternations between morphophones themselves—substitutions, alterations, and replacements.