I. ˈsəb+ˌ- noun
Etymology: sub- + group
: a subordinate group usually of individuals sharing some common quality that makes them distinguishable from other members of a major group to which they belong
the Britannic subgroup of the Celtic languages — Isidore Dyen
the subgroup of the professional criminal … has basic similarities … to the subgroup of the industrialist — R.K.Merton
II. | ̷ ̷| ̷ ̷ transitive verb
: to divide into subgroups
III. noun
: a subset of a mathematical group that is itself a group