[…] the only function of a morph is to represent a morpheme.
- Hockett (1958), a pag.293

Each representation is a ‘morph’; all the morphs which represent some given morpheme are called ‘allomorphs’ of that morpheme. Thus /sél/ and /s...l/ are both allomorphs of the morpheme {‘sell’}.
- Hockett (1958), a pag.272

Two morphs cannot be allomorphs of a single morpheme if they contrast. […]. (II) Two morphs cannot be allomorphs of a single morpheme unless they have the same meaning. […]. (III) Even if other criteria are satisfactorily met, one does not assign two morphs to a single morpheme unless the resulting morpheme fits into the emerging grammatical picture of the language in a sensible way.
- Hockett (1958), a pag.274