In computational learning theory, the teaching dimension of a concept class C is defined to be max c ∈ C { w C ( c ) } {displaystyle max _{cin C}{w_{C}(c)}} , where w C ( c ) {displaystyle {w_{C}(c)}} is the minimum size of a witness set for c in C. In computational learning theory, the teaching dimension of a concept class C is defined to be max c ∈ C { w C ( c ) } {displaystyle max _{cin C}{w_{C}(c)}} , where w C ( c ) {displaystyle {w_{C}(c)}} is the minimum size of a witness set for c in C. The teaching dimension of a finite concept class can be used to give a lower and an upper bound on the membership query cost of the concept class. In Stasys Jukna's book 'Extremal Combinatorics', a lower bound is given for the teaching dimension: Let C be a concept class over a finite domain X. If the size of C is greater than then the teaching dimension of C is greater than k.