For example, the English verbs arrive and run differ in their lexical aspect since the former describes an event which has a natural endpoint while the latter does not.
Although lexical aspect need not be marked morphologically, it has downstream grammatical effects, for instance that arrive can be modified by "in an hour" while believe cannot.
Zeno Vendler classified verbs into four categories on whether they express "activity", "accomplishment", "achievement" or "state".
[1][2] In his discussion of lexical aspect, Bernard Comrie included the category semelfactive or punctual events such as "sneeze".
Of the durative verbs, states are unique as they involve no change, and activities are atelic (that is, have no "terminal point") whereas accomplishments are telic.