well-bred
Having very good manners and polite, respectful behavior.
Well-bred describes someone who has been taught good manners and knows how to behave properly in different situations. A well-bred person says please and thank you, treats others with respect, and understands social expectations like not interrupting when someone else is speaking or chewing with their mouth closed at dinner.
The term originally referred to people from wealthy or aristocratic families who received careful instruction in etiquette and proper behavior. Today, the word has a somewhat old-fashioned ring to it, but the idea behind it remains important: having good manners and treating others with consideration.
You might also hear well-bred used to describe animals, especially horses or dogs, that come from excellent bloodlines and have been carefully raised. A well-bred show dog might come from champion parents and receive extensive training.
When applied to people, well-bred focuses on learned behavior and manners rather than family background. A well-bred student might hold the door for someone carrying heavy books or know how to introduce two people who haven't met before. These courtesies make social interactions smoother and more pleasant for everyone involved.