[...] a language, by some recognizable phonetic or grammatical feature, groups a number of its forms into 'form-classes' [...]
- Bloomfield (1935), a pag.146

Form-classes, like other linguistic phenomena, can be defined, not in terms of meaning, but only in terms of linguistic (that is, lexical or grammatical) features.
- Bloomfield (1935), a pag.268

All the forms which can fill a given position thereby constitute a 'form-class'.
- Bloomfield (1935), a pag.185

Lexical forms which have any function in common belong to a common 'form-class.'
- Bloomfield (1935), a pag.265

The form-class of a lexical form is determined [...] by the structure and constituents of the form, by the inclusion of a special constituent (a marker), or by the identity of the form itself.
- Bloomfield (1935), a pag.268