Paternal describes anything related to being a father or coming from the father's side of a family. Your paternal grandfather is your dad's father, while your paternal grandmother is your dad's mother. If you have your dad's last name, it's your paternal surname.

The word also describes fatherly qualities or behaviors. A teacher who shows paternal concern for students cares for them with the protective, guiding warmth associated with fathers. A coach might take a paternal interest in helping players develop not just their skills but their character. When someone acts in a paternal way, they're being protective, supportive, and nurturing like a good father would be.

The opposite word is maternal, which relates to mothers and the mother's side of the family. Your maternal grandparents are your mom's parents. Together, these words help us describe different branches of our family trees and different kinds of caring relationships in our lives.