(uncountable) The state of being relative to something else; the absence of universally applicable rules or standards; relativism; an instance of this.

(uncountable, physics) A noun "relativity" represents the principle that the laws of physics should be the same for all observers, specifically referring to the reliance of physical phenomena on the relative motion between an observer and the thing observed, as developed by albert einstein in his theories of special relativity and general relativity.

(countable, chiefly in the plural) A noun "relativity" represents an evaluation of similarities and differences between things, a comparison, and a difference in position or status between things.