Authority
Etymology
From Latin “auctoritas,” from “auctor” — an originator or author — from “augere,” “to increase.” Authority and author share a root: the one with authority was the one who originated or vouched for something, whose word made it grow into fact. The link explains why we still speak of an “authority” on a subject.
noun · /uh-THOR-ih-tee/
The recognized right to command, decide, or be believed — power that others accept as legitimate.
What it names
Use it when what matters is not who can force an outcome but who is entitled to, and whether people acknowledge that entitlement.
Example
The nurse had no formal authority over the surgeon, but her twenty years on the ward gave her word real weight.
Related idea
Authority is power that is recognized as rightful. Strip away the recognition and you are left with mere coercion; strip away the power and you have a claim no one obeys.
noun · /uh-THOR-ih-tee/
A recognized expert or definitive source on a subject.
What it names
a leading expert or trusted source
Example
She is a world authority on medieval coins.
Related idea
One believed not because they command but because they know.
noun · /uh-THOR-ih-tee/
A public body with power over a particular area.
What it names
a governing agency or body
Example
The transit authority raised fares; report it to the authorities.
Related idea
Here authority names the body itself — a transit or housing authority — rather than the right to command; the area it governs is its jurisdiction.