noun
Mathematical term: a subset of a group that is itself a group under the same operation.
群Gの部分群Hを考える。
Consider a subgroup H of the group G.
この集合は部分群の条件を満たす。
This set satisfies the conditions for a subgroup.
正規部分群 is a normal subgroup, a special type of subgroup invariant under conjugation.
Compound of 部分 (bubun, 'part') and 群 (gun, 'group'), a direct translation of the mathematical term 'subgroup'.