A value of Aspect Property (also called Nonstative aspect) assigned to the designated element in the clause when the meaning selected for the clause is that which indicates that the situation spoken about has internal temporal structure, it cannot be regarded as habitual, and reference is made to this situation in progress. Hence, progressiveness can be defined as the combination of progressive meaning with nonstative meaning, and it can be regarded as a sub-type of continuousness (which, in turn, is a sub-type of imperfectivity). Since languages have different criteria for classifying predicates as stative or not, they may have different rules for determining when explicitly progressive forms can be used.
Typically, for an aspect value to be labelled as Progressive, the aspectual meaning has to minimally express progressiveness, although it may additionally express other temporal, aspectual, or modal meanings, or actionality distinctions. [Kibort 2008c: 8]