The extension is a subset A of the set of objects G and the intension is a subset B of the set of attributes M. We call the pair (A,B) a formal concept if each object of the extension has all the properties of the intension.
for the data shown in Figure 1, the pair ({Gropius, Breuer}, {Urban Planner, Architect}) represents a formal concept: each of the members of the extension possesses all the attributes mentioned in the intension.