[...] other relational concepts are either merely parasitic (gender throughout; number in the demonstrative, the adjective, the relative, and the verb) or irrelevant to the essential syntactic form of the sentence (number in the noun; person; tense).
- Sapir (1921), a pag.97

'Pure Relational Concepts' [...]: normally expressed by affixing non-radical elements to radical elements [...] or by their inner modification, by independent words, or by position; serve to relate the concrete elements of the proposition to each other, thus giving it definite syntactic form.
- Sapir (1921), a pag.101

[...] the 'part of speech' reflects not so much our intuitive analysis of reality as our ability to compose that reality into a variety of formal patterns. A part of speech outside of the limitations of syntactic form is but a will o' the wisp.
- Sapir (1921), a pag.119