morphophonemen.

1934 M. Swadesh in Language 10 129 Morphologically distinct phonemes are called morpho-phonemes. A morpho-phoneme is one of a class of like phonemes considered as components of actual morphemes which behave alike morphologically, i.e., have a like place in the same mutation series.

1939 L. Bloomfield in Travaux du Cercle Linguistique de Prague VIII. 106 The morphophoneme u seems to occur in only one suffix.

1947 C. F. Hockett in Language 23 323 Morphophonemic statements may involve morphophonemes—that is, the symbols used for phonemes, plus supplementary ones, with special definitions as to phonemic value under varying circumstances—or they may not.

1957 N. Chomsky Syntactic Struct. iv. 33 The elements that figure in the rules can be classified into a finite set of levels (e.g. phonemes and morphemes; or, perhaps, phonemes, morphophonemes, and morphemes).

1968 Language 44 508 The major thesis of this paper is that the most efficient description of morpheme alternants requires the use of morphophonemes, and, moreover, that these morphophonemes do in fact constitute psychologically real units.

1988 Amer. Speech 43 269 I offer caution to readers who are less familiar with the breadth of relevant literature on this morphophoneme.