In terms of aspect, Vendler (1967) distinguishes four classes of verbs: states, activities, accomplishments and achievements. Heinamaki (1974), however, proposes the three-part distinction: duratives (states and activities), non-duratives (achievements) and accomplishments, and describes that all three types of verbs can appear in until - clauses. This remark on the verbs seems to be inconsistent with the facts. Non-duratives and accomplishments can appear freely in until -clauses whereas verbs in progressive aspect, which are considered to be duratives, are not always allowed.
In this paper, I propose the semantics of verbs in until -clauses, which stipulates that verbs in the clauses should have two interrelated grounds for the appearance: (A) With reference to tense, they have a temporal, instantaneous reference time (R1) to designate the terminal point of the main clause; and (B) Aspectually, they have a potential starting or end point (R0) which is anchored by R1 on the time line. Then, it is shown, with the aid of these stipulations, that accomplishments and achievements in until -clauses are unmarked cases where R0 is marked with R1 on the time line while verbs in progressive are marked ones where R0 is not marked with R1. In the former, R1 is simultaneous with R0 on the time line. But, in the latter, R1 does not fall on R0 and there is a time lag between them. The grammaticality for the latter is guaranteed by the fact that R0 is a reference point from which R1 is easily accessible. I also point out that seemingly stative verbs should not be recognized as states but as achievements (or accomplishments) in until -clauses.