A pair ('; ) is called an isoclinism between groups G and H if ' is an isomorphism from G=Z(G) to H=Z(H), is also an isomorphism from G0 to H0 and ([g1; g2]) = [h1; h2] whenever hi 2 '(giZ(G)), for all gi 2 G, hi 2 H, i 2 f1; 2g. The commutativity degree of a group G is the probability that a randomly chosen pair of elements in a group G commutes. In this talk, we will give a relation between the notion of the isoclinism and commutativity degree and will also generalize them to relative n-isoclinism and relative n-th nilpotency degree, re- spectively.

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