adj.
   - done in accordance with rules of convention or etiquette. ▸having a conventionally recognized form, structure, or set of rules: ![]()  he had little formal education. 
▸of or denoting a style of writing or public speaking characterized by more elaborate grammatical structures and more conservative and technical vocabulary. 
- officially recognized:![]()  a formal complaint. 
- of or concerned with outward form rather than content. ▸having a form or appearance but no true function: ![]()  the committee stage would be purely formal. 
▸relating to linguistic or logical form as opposed to function or meaning. 
n.
 N. Amer. an evening dress. 
▸an occasion on which evening dress is worn.
Derivative
  
  Etymology
  ME: from L. formalis, from forma (see form).