foster-child vs foster child

foster-child and foster child both are nouns.

Word	Noun	Adjective	Verb	Adverb
foster-child	Yes	No	No	No
foster child	Yes	No	No	No

As nouns, foster-child and foster child are synonyms defined as:

Other synonyms of foster-child include fosterling.

foster-child (noun)	foster child (noun)
a child who is raised by foster parents	a child who is raised by foster parents