真しん部ぶ分ぶん集しゅう合ごう

noun

proper subset

Mathematical term: a subset that is strictly contained in another set, i.e., all elements of A are in B, but B has at least one element not in A.

• AがBの真ま部ぶ分ぶん集しゅう合ごうであるとき、A⊂Bと表あらわす。

  When A is a proper subset of B, we write A⊂B.