[...] we believe that English nouns and verbs share a pattern which we call "s-form", consisting of the stem followed by "-s" although an "s-form" verb is clearly very different in syntax and semantics from an "s-form" noun. This notion of "X-form" is important for the analysis of systematic sincretism [...]. This concept is new to WG. X-forms mediate between the stem and the whole.
- Creider & Hudson (2004), Pag. 449