Algebra - vocabulary

 /ˈsʌbˌɡruːp/

Let (G, *, ',e) be a group. Let H be a subset of G. We say, that H is a subgroup of G if e is element of H, and for every a,b elements of H are a*b and a' elements of H.

For pronunciation: https://dictionary.cambridge.org/dictionary/english/subgroup