foster-parent vs guardian

foster-parent and guardian both are nouns.

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

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

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
guardian: a person who cares for persons or property

Other hypernyms of foster-parent include defender, protector, shielder.

foster-parent (noun)	guardian (noun)
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	a person who cares for persons or property