late 14c., practisen, "to follow or employ" a course of action; c. 1400, "to do, put into action or practice;" from Old French pratiser, practiser "to practice," alteration of practiquer, from Medieval Latin practicare "to do, perform, practice," from Late Latin practicus "practical," from Greek praktikos "practical" (see practical).

From early 15c. as "to carry on a profession," especially medicine; also "to do or perform repeatedly or habitually with the object of acquiring skill, to learn by repeated performance;" from mid-15c. as "to perform, work at, exercise." Intransitive sense of "perform certain acts repeatedly, train one's self" is by 1590s. Sense of "to cause to practice, teach by exercise, train, drill" is from 1590s. Related: Practiced; practicing.

early 15c., practise, "practical aspect or application," originally especially of medicine but also alchemy, education, etc.; from Old French pratiser, from Medieval Latin practicare (see practice (v.)). It largely displaced the older word, practic, which survived in parallel into 19c. From early 15c. it began to be assimilated in spelling to nouns in -ice.

Sense of "habit, frequent or customary performance" is from c. 1500. Meaning "exercise for instruction or discipline" is from 1520s. Sense of "action, the process of accomplishing or carrying out" (opposed to speculation or theory) is from 1530s. The meaning "regular pursuit of some employment or business" is from 1570s. In 16c.-17c. it also was used in an evil sense, "conspiracy, a scheme."

Practice is sometimes erroneously used for experience, which is a much broader word. Practice is the repetition of an act : as, to become a skilled marksman by practice. Experience is, by derivation, a going clear through, and may mean action, but much oftener views the person as acted upon, taught, disciplined, by what befalls him. [Century Dictionary]

also practised, "expert, skilled through practice," 1540s, past-participle adjective from practice (v.).

also practising, 1620s in reference to professions; from 1906 in reference to religions (Catholics); present-participle adjective from practice (v.).

also unpractised, 1550s, "unexpert," of persons, from un- (1) "not" + past participle of practice (v.). From 1530s as "not done, untried."

the usual spelling outside American English of practice as a verb. It also is the form of the verb in the U.S.-produced "Century Dictionary" (1889). Related: Practised; practising.

1670s, "bad treatment of disease, pregnancy, or bodily injury from ignorance, carelessness, or with criminal intent," a hybrid coined from mal- + practice (n.). Also used for "illegal action by which a person seeks a benefit for himself while in a position of trust" (1758).

"a practitioner; one who practices (as distinguished from one who theorizes," originally also practitian, c. 1500, from Old French practicien (Modern French praticien), from Late Latin practicus "fit for action," (see practice (v.)). An earlier word was practisour (late 14c.).

1540s, "one who acquires knowledge from actual practice;" a hybrid formed from practitian "practitioner" (c. 1500; see practician), with redundant ending on model of parishioner. Meaning "one engaged in the actual practice of an art or profession" is from 1550s. Johnson has as a secondary sense "One who uses any sly or dangerous arts" (compare practice (n.)). A general practitioner originally was "someone who practices both medicine and surgery."

1580s, "practice or discipline for a specific purpose," from Medieval Latin praxis "practice, exercise, action" (mid-13c., opposite of theory), from Greek praxis "practice, action, doing," from stem of prassein, prattein "to do, to act" (see practical). From 1610s as "a collection of examples for practice." In 20c. given a particular sense in Marxist jargon.