Other forms: joints
A joint is a place where two things meet and can move — the knee, the elbow, the hinge of a folding chair. In carpentry and plumbing it is where two pieces are fixed together, and there it usually does not move at all.
As an adjective it means shared between two or more: a joint account, a joint decision, joint winners. That sense is common in banking and law and is easy to miss because the noun is so much better known. Two food senses are worth having: a joint of meat is a large piece for roasting, which is British, and a joint in informal speech is a place, usually a slightly shabby one. The verb, to joint, means to cut meat up at the joints.
1nounjointA place in the body where two bones meet and can bend.
“Her joints ache in cold weather.”
synonyms: articulation
3nounfixedA place where two parts are fixed together.
“The joint had come loose and the whole thing wobbled.”
4nounlargeA large piece of meat for roasting.
“She put the joint in at eleven.”
Too few real examples of this word to estimate which sense is commonest.
joint is a place where things meet.
Old French joint is the past participle of joindre, to join, from Latin iungere — the same verb behind junction, conjunction and yoke. A joint is simply a joined thing, and the noun has never meant anything else.
Proto-Indo-European
*yewg-
Latin
iūnctus
Old French
joint — joint of the body
Middle English
joynt
English, today
joint
The noun is from Middle English joynt (attested since the late 13th century), from Old French joint (“joint of the body”) (attested since the 12th century). The adjective (attested since the 15th century) is from Old French jointiz. Both Old French words are from Latin iūnctus, the past participle of iungō. See also join, jugular, junction. Displaced Old English fōg and partially displaced English lith. The meaning of "building, establishment", especially in connection with shady activities, appeared in Anglo-Irish by 1821 and entered general American English slang by 1877, especially in the sense of "opium den". The sense "marijuana cigarette" is attested since 1935. The development to meaning "any thing" also happened to the Scots and Memphian form junt and the Mid-Atlantic/Philadelphian form jawn.
Etymology from Wiktionary, CC BY-SA