A distinction is made between (1) stems, which may consist of any number of morphemes but which include a root and underlie further formation, and (2) root.
- Nida (1949), a pag.46

Stems, which consist of a root or a root plus some other morpheme, are by definition always bound, e.g. '-ceive' (cf. 'receive') and 'recep-' (cf. 'reception'), 'manli-' (cf. 'manliness') and 'formaliz-' (cf. 'formalizer').
- Nida (1949), a pag.81

All bound roots are stems, but not all stems (they are all bound) are roots. A stem is composed of (1) the nucleus, consisting of one or more roots, or (2) the nucleus plus any other nonroot morphemes, except the last 'structurally added' morpheme that results in a word. The form 'man-' in 'manly' is at the same time a root and a stem.
- Nida (1949), a pag.83