late 14c., "pertaining to form or arrangement;" also, in philosophy and theology, "pertaining to the form or essence of a thing," from Old French formal, formel "formal, constituent" (13c.) and directly from Latin formalis, from forma "a form, figure, shape" (see form (n.)). From early 15c. as "in due or proper form, according to recognized form," As a noun, c. 1600 (plural) "things that are formal;" as a short way to say formal dance, recorded by 1906 among U.S. college students.

1590s, "give an appearance of being to," from formal + -ize. Meaning reduce to form" is from 1640s; sense of "render formal" is from 1855. Related: Formalized; formalizing.

late 14c., "in good form, in an orderly manner," also "by kind," from formal + -ly (2). Meaning "in prescribed or customary form" is from 1560s.

1840, "strict adherence to prescribed forms," from formal + -ism. Used over the years in philosophy, theology, literature, and art in various senses suggesting detachment of form from content, or spirituality, or meaning; or belief in the sufficiency of formal logic. Related: Formalist.

mid-15c., "lacking form; not in accordance with the rules of formal logic," from in- (1) "not, opposite of" + formal (adj.). Meaning "irregular, unofficial, not according to rule or custom" is from c. 1600. Sense of "done without ceremony" is from 1828. Related: Informally.

1530s, "agreement as to form," from formal + -ity or else from French formalité (15c.) or Latin formitalitatem. Sense of "conformity to established rule" is from 1590s; meaning "something done for the sake of form" is from 1640s. Related: Formalities.

Japanese art of formal flower arrangement, 1901, from Japanese, from ikeru "to keep alive, arrange" + hana "flower."

formal term of address to a lady, 1590s, see madam, which is an earlier borrowing of the same French phrase. Originally a title of respect for a woman of rank, now given to any married woman. It is more formal or affected than madam. OED recommends madam as an English title, madame in reference to foreign women.

early 14c., "a quarrel, dispute, disagreement" (now archaic), from Old French debat, from debatre(see debate (v.)). Sense of "contention by argument" is from late 14c., that of "a formal dispute, a debating contest, interchange of arguments in a somewhat formal manner" is perhaps from early 15c.

"act of pronouncing; a proclamation or formal announcement," 1590s, from pronounce + -ment.