  In this note the usual Goursat lemma, which describes subgroups of the direct
product of two groups, is generalized to describing subgroups of a direct
product $A_1\times A_2 \times...\times A_n$ of a finite number of groups. Other
possible generalizations are discussed and applications characterizing several
types of subgroups are given. Most of these applications are straightforward,
while somewhat deeper applications occur in the case of profinite groups,
cyclic groups, and the Sylow $p$-subgroups (including infinite groups that are
virtual $p$-groups).
