means A relationship in which two or more people share the work, the profits, and the responsibilities of a common venture, whether a business, a project, or a life together.

from Built from 'partner,' which arrived in English through Anglo-French as an alteration of 'parcener' — a legal term for a co-heir who took a 'parcel' or share of an estate. The root traces back to Latin 'pars, partis,' meaning 'a part' or 'share,' the same ancestor behind 'portion' and 'party.' The folksy '-ner' ending was likely reshaped by the influence of 'part' itself, so the word literally means 'one who holds a share.' Tack on '-ship' — the old Germanic suffix denoting a state or condition — and you get the whole arrangement of sharing made into a noun.