fosterling vs foster-child

fosterling and foster-child both are nouns.

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

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

Other synonyms of fosterling include foster child.

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