foster-mother vs foster-parent

foster-mother and foster-parent both are nouns.

Word	Noun	Adjective	Verb	Adverb
foster-mother	Yes	No	No	No
foster-parent	Yes	No	No	No

As nouns, foster-parent is a hypernym of foster-mother; that is, foster-parent is a word with a broader meaning than foster-mother:

foster-mother: a woman who is a foster parent and raises another's child
foster-parent: a person who acts as parent and guardian for a child in place of the child's natural parents but without legally adopting the child

Other hypernyms of foster-mother include foster parent.

foster-mother (noun)	foster-parent (noun)
a woman who is a foster parent and raises another's child	a person who acts as parent and guardian for a child in place of the child's natural parents but without legally adopting the child