adjective

1. of external form or structure, rather than nature or content
2. of the internal form; relating to the intrinsic or essential character or nature
3. of or according to prescribed or fixed customs, rules, ceremonies, etc. a formal wedding
4. 1. having the appearance of being suitable, correct, etc., but not really so
   2. stiff in manner; not warm or relaxed
5. 1. designed for use or wear at ceremonies, elaborate parties, etc. formal dress
   2. requiring clothes of this kind a formal dance
6. done or made in orderly, regular fashion; methodical
7. very regular or orderly in arrangement, pattern, etc.; rigidly symmetrical a formal garden
8. done or made according to the forms that make explicit, definite, valid, etc. a formal contract
9. designating education in schools, colleges, etc.
10. designating or of the level of language usage characterized by expanded vocabulary, complete syntactic constructions, complex sentences, etc.

Etymology: ME < L formalis < forma, form

noun

1. a formal dance or ball
2. a woman's evening dress