for·mal 
(fôrməl)
(fôrməl)adj.
1.
a. Relating to or involving outward form or structure, often in contrast to content or meaning.
b. Being or relating to essential form or constitution: a formal principle.
2. Following or being in accord with accepted or prescribed forms, conventions, or regulations: had little formal education; went to a formal party.
3.
a. Characterized by strict or meticulous observation of forms; methodical: very formal in their business transactions.
b. Stiffly ceremonious: a formal greeting.
4. Characterized by technical or polysyllabic vocabulary, complex sentence structure, and explicit transitions; not colloquial or informal: formal discourse.
5. Having the outward appearance but lacking in substance: a formal requirement that is usually ignored.
n.
Something, such as a gown or social affair, that is formal in nature.
[Middle English, from Latin fōrmālis, from fōrma, shape.]
formal·ly adv.
formal·ness n.