Definition of foster- in English:

foster-

combining form

1Denoting someone that has a specified family connection through fostering: foster-parent foster-child
1.1Involving or concerned with fostering a child: foster care

Origin

foster-father, foster-mother, foster-child, and foster-brother all date from Old English. Foster-mother has also been used to mean a wet nurse, her husband being foster-father to the child she fed, and a foster-brother or -sister one reared at the same breast.

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Word of the day anastrophe
Pronunciation: əˈnastrəfi
noun
the inversion of the usual order of words...