We [...] know of four distinct formal types of word: 'A' (Nootka 'hamot');' A + (0)' ('sing', 'bone'); 'A + (b)' ('singing'); '(A) + (b)' (Latin 'hortus').
- Sapir (1921), a pag.29

It would be possible to demonstrate the existence of a vast number of formal types of [...] partial duplication [...]
- Sapir (1921), a pag.77

[...] phonetic changes comprised under the term 'umlaut', [...] struck the German language at a time when the general drift to morphological simplification was not so strong but that the resulting formal types (e.g., 'Fuss: Füsse'; 'fallen' 'to fall': 'fällen' 'to fell' [...]) could keep themselves intact [...]
- Sapir (1921), a pag.190