Zeno Vendler (1957) classified verbs into four categories: those that express "activity", "accomplishment", "achievement" and "state". Activities and accomplishments are distinguished from achievements and states in that the former allow the use of continuous and progressive aspects. Activities and accomplishments are distinguished from each other by boundedness: activities do not have a terminal point (a point before which the activity has taken place and after which cannot continue – for example "John drew a circle") whereas accomplishments do.