formal - noun

a lavish dance requiring formal attire

a gown for evening wear

formal - adjective

• being in accord with established forms and conventions and requirements (as e.g. of formal dress)
• (of spoken and written language) adhering to traditional standards of correctness and without casual, contracted, and colloquial forms
• characteristic of or befitting a person in authority
• represented in simplified or symbolic form
• logically deductive
• refined or imposing in manner or appearance; befitting a royal court

formal - thesaurus

ball   conventional   courtly   schematic   stately