Meaning of “maternal” - Learner’s Dictionary

maternal

adjective uk us /məˈtɜːnəl/
LIKE A MOTHER

like a mother:

I've never had much of a maternal instinct (= natural ability to be a good mother).
MOTHER'S FAMILY [ always before noun ]

A maternal relation is part of your mother's family:

He's my maternal grandfather.

(Definition of “maternal” from the Cambridge Learner’s Dictionary © Cambridge University Press)