Meaning of “formal” - Learner’s Dictionary

formal

adjective us uk /ˈfɔːməl/
formal dressBritish people are often perceived as being very formal.He sounded very formal.She spoke in a very formal manner.The dinner was a formal affair.
SERIOUS

B2 used about clothes, language, and behaviour that are serious and not friendly or relaxed:

a formal dinner party
IN SCHOOL [ always before noun ]

Formal education, training, etc happens in a school or college:

Tom had little formal schooling.

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