A value of Aspect Property assigned to the designated element in the clause when the meaning selected for the clause is that which indicates that the event spoken about is to be looked at from inside, from within its temporal boundaries; imperfective aspect is crucially concerned with the internal temporal structure of the event [Comrie 1976: 16ff].
Typically, for an aspect value to be labelled as Imperfective, the aspectual meaning has to minimally express the imperfective viewpoint, although it may additionally express other temporal, aspectual, or modal meanings, or actionality distinctions.
Imperfective aspectual meaning can be further subdivided into two types: habitual meaning and continuous meaning. These two aspectual meanings may or may not be grammaticalised as separate aspect values. [Kibort 2008c: 7]