Necessary according to etiquette, protocol or fashion.

(geometry) A right triangle.

(geometry) A triangle having a right angle as one of its interior angles.

(algebra) An element of a structure that produces an identity mapping when applied on the right.

(law) The exclusive rights pertaining to the ownership and possession of a given piece of property.

One whose occupation is to fit the rigging of a ship or of a counterweight system.

(paraskiing) Ellipsis of outrigger.

Showing, causing, or favoring rigour/rigor; scrupulously accurate or strict; thorough. / Severe; intense.

(intransitive, US slang) To turn right, to take a right turn.

(law) The power, granted by the government to persons, to allow or disallow others from taking certain actions (through legal force)