Usitative

[Rudy Troike]

Mia,

      Good question. It's commonplace for languages to evolve
"grammaticalization"
of certain distinctions/features, while other languages express these
distinctions/features "periphrastically" (to use a good term from traditional
grammar), others lexically, and still others not at all. A good example is
plural, which most European languages express grammatically, while other
languages such as some of those in South-east Asia, express the 
distinction only
lexically, by using numbers or quantifier words.

      Scott's example of English "used to" belongs in the grammatically gray
(grey?) area of what Martin Joos called "quasi-modals". These involve the
use of verbs which have been "bleached" of their primary meaning, and are
in the process of becoming purely grammatical markers (we are inhibited in
seeing this because of the practice of putting white spaces around "words"
(whatever those are)). Examples are things like "be going to", "have to",
"want to" (= desiderative), "start" (=inceptive), "stop" (=cessative), + a
main Verb. Often these are reduced phonologically, as in "ahmonna" ('I'm
going to'), Scott's "usta", and "hafta", "wanna", etc., showing further
(again obscured by spelling) how these are becoming grammaticalized.

      Whether something is clearly part of the purely grammatical structure
of a language, or somewhere on the slippery slope toward becoming
grammaticalized, may be an accident of the historical point at which
we examine the language, since a thousand years earlier or later, the
language might show very different grammatical/structural features.

      Rudy Troike