influence is the capacity to produce an effect on someone or something by indirect or intangible means — sway exerted without any apparent use of force or direct command.
Influence travels through 📝authority, expertise, social position, trust, or the shaping of narratives and environments. Social psychology distinguishes informational influence, where a person adopts a belief because they take others to hold better information, from normative influence, where a person conforms to keep a group's approval. It can be formal, attached to an office or an institution, or informal, arising from charisma and relationship. Robert Cialdini's 📝Influence: The Psychology of Persuasion catalogues the levers most often named — reciprocity, commitment, social proof, authority, liking, and scarcity — and the same mechanisms underwrite the modern 📝influencer, whose sway is measured in reach rather than office.
The word arrived in late fourteenth-century English as an astrological term for an ethereal fluid streaming from the stars and acting on human character and destiny. It came through Old French from Medieval Latin influentia, "a flowing in," from influere — in-, "into," plus fluere, "to flow." The sense of unseen pressure exerted by people rather than planets is recorded by the 1580s and the general meaning by about 1650. "Under the influence," meaning intoxicated, is attested from 1866, a survival of the older idea of a substance flowing in and taking over.
Influence is narrower than 📝power, which includes the ability to compel outright; what distinguishes influence is that compliance remains, at least formally, voluntary. It differs from authority, which is positional and conferred, in that influence must be earned and can be held by someone with no title at all. And it is separable from 📝manipulation, which produces the same effect by concealing its own operation — the line between them lies in whether the person being moved could see the move being made.