[…] members of the construction sometimes or never constitute by themselves the whole utterance in which they are contained. Or we can say that almost all English utterances contain at least one of the free classes ('A, N ¹, V ¹, D', etc.) or the bound class 'S' […] with zero or more morphemes of the other bound classes ('Na', several 'T' and 'P', etc.) grouped around each of these.
- Harris (1951), a pag.329