formal

a lavish dance requiring formal attire

represented in simplified or symbolic form

a gown for evening wear

refined or imposing in manner or appearance; befitting a royal court

being in accord with established forms and conventions and requirements (as e.g. of formal dress)

“pay one's formal respects”

characteristic of or befitting a person in authority

“formal duties”

logically deductive

“formal proof”

adhering to traditional standards of correctness and without casual, contracted, and colloquial forms

“the paper was written in formal English”