In some morpheme units the alternants are the same except for one or two phonemes […]. In other units there are many alternants, all (or most) having some phonemic structure in common […]. In both cases we say that the alternants differ in only part of their phonemic sequence. In other units, however, […] the alternants differ entirely.
- Harris (1942a), a pag.175

When a morpheme unit occurs in a given context, the alternant which appears there is determined by the environment of neighboring alternants. Each alternant of that unit occurs only in the neighborhood of particular other alternants; and often, if we investigate each of the morphemes in whose neighborhood the given alternant occurs, we will find that there is a common feature to all of them.
- Harris (1942a), a pag.175

Every statement, general or particular, about the alternants must contain three pieces of information: (a) what is the difference between the alternants; (b) in what environments does each alternant occur; (c) in what units does the difference occur. It is seen that various groupings of alternants into units differ on these three counts.
- Harris (1942a), a pag.180

In many morpheme units there is no recognizable similarity between the alternants and the environments in which they occur; e.g. between 'am' and 'I', between '–i' (alternant of 'am') and /-z/ ‘3d sg. pres.’, between /ej/ ~ /u/ and 'take'.
- Harris (1942a), a pag.177