adj. & n.
adj. 1 used or done or held in accordance with rules, convention, or ceremony (formal dress; a formal occasion). 2 ceremonial; required by convention (a formal call). 3 precise or symmetrical (a formal garden). 4 prim or stiff in manner. 5 perfunctory, having the form without the spirit. 6 valid or correctly so called because of its form; explicit and definite (a formal agreement). 7 in accordance with recognized forms or rules. 8 of or concerned with (outward) form or appearance, esp. as distinct from content or matter. 9 Logic concerned with the form and not the matter of reasoning. 10 Philos. of the essence of a thing; essential not material.
n. US 1 evening dress. 2 an occasion on which evening dress is worn. formally adv. formalness n.
[ ME f. L formalis (as FORM) ]