relativity

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The quality or state of being relative.
2. n. A state of dependence in which the existence or significance of one entity is solely dependent on that of another.
3. n. Physics Special relativity.
4. n. Physics General relativity.

Century Dictionary and Cyclopedia

1. n. The character of being relative; relativeness; the being of an object as it is by force of something to which it is relative.
2. n. Specifically Phenomenality; existence as an immediate object of the understanding or of experience; existence only in relation to a thinking mind.
3. n. The doctrine that it is impossible to have knowledge of anything except by means of its relations to the mind, direct and indirect, cognized as relations.
4. n. The doctrine of phenomenalism, that only appearances can be known, and that the relations of these appearances to external substrata, if such there be, are completely incognizable. This doctrine is sometimes associated with a denial of the possibility of any knowledge of relations as such, or at least of any whose terms are not independently present together in consciousness. It would therefore better be denominated the doctrine of the impossibility of relativity of cognition.
5. n. The doctrine that we can only become conscious of objects in their relations to one another. This doctrine is almost universally held by psychologists.

Wiktionary

1. n. The state of being relative to something else.
2. n. physics The principle that the laws of physics should be the same for all observers.
3. n. physics Either of two theories (special relativity or general relativity) developed by German-American physicist Albert Einstein. Also called Einsteinian relativity.

GNU Webster's 1913

1. n. The state of being relative.
2. n. One of two theories (also called theory of relativity) proposed by Albert Einstein, the special theory of relativity, or the general theory of relativity. The special theory of relativity or special relativity is based on the proposition that the speed of light is a constant no matter how observed, and is independent of the motion of the observer. From this follows several principles, such as the increase of mass with velocity (which has been confirmed: see relativistic mass equation) and the impossibility of acceleration to a speed greater than that of light; the equivalence of mass and energy, expressed by the famous equation E = mc2; and time dilation, which is the apparent slowing of a clock in a system, as observed by an observer in a system moving relative to the clock. The general theory of relativity is based on the proposition that there is no physical difference between gravitational force and the force produced by acceleration. From this follow several results, of which the bending of light rays in a gravitational field and the equivalence of the inertial and gravitational masses have been verified. The possible existence of black holes (believed by many astronomers to have been adequately proven) is another consequence of the theory.

WordNet 3.0

1. n. (physics) the theory that space and time are relative concepts rather than absolute concepts
2. n. the quality of being relative and having significance only in relation to something else