relativity

noun

rel·​a·​tiv·​i·​ty ˌre-lə-ˈti-və-tē 

plural relativities

1

a

: the quality or state of being relative

b

: something that is relative

2

: the state of being dependent for existence on or determined in nature, value, or quality by relation to something else

3

a

: a theory which is based on the two postulates (1) that the speed of light in a vacuum is constant and independent of the source or observer and (2) that the mathematical forms of the laws of physics are invariant in all inertial systems and which leads to the assertion of the equivalence of mass and energy and of change in mass, dimension, and time with increased velocity

called also special relativity, special theory of relativity

b

: an extension of the theory to include gravitation and related acceleration phenomena

called also general relativity, general theory of relativity

4

: relativism sense 1b

Examples of relativity in a Sentence

Recent Examples on the Web

Because black hole gravity is so strong, anything that takes place within the event horizon can’t ever be observed from outside the black hole, according to relativity. —Lyndie Chiou, Wired News, 20 Apr. 2025

Back then, Schroeder said, there was a large margin of error for the relativity new science of carbon dating. —Mary Walrath-Holdridge, USA TODAY, 21 Mar. 2025

Perhaps, then, the answer is to modify, change or update relativity itself to gain a new understanding of gravity rather than hypothesizing mysterious dark substances and forces. —Paul M. Sutter, Scientific American, 26 Feb. 2025

Within just a few years, Einstein would publish his theory of relativity and launch an entirely new era of physics. —Dr. Diane Hamilton, Forbes.com, 6 Apr. 2025

Word History

First Known Use

circa 1834, in the meaning defined at sense 1a

Phrases Containing relativity

• general relativity
• general theory of relativity
• special relativity
• special theory of relativity

Rhymes for relativity

• absorptivity
• affectivity
• collectivity
• conductivity
• connectivity
• corrosivity
• creativity
• diffusivity
• directivity
• effectivity
• emissivity
• exclusivity

Kids Definition

relativity

noun

rel·​a·​tiv·​i·​ty ˌrel-ə-ˈtiv-ət-ē 

plural relativities

1

: the quality or state of being relative

especially : dependence on something else

2

a

: a theory in physics that considers mass and energy to be equal and that states that a moving object will experience changes in mass, size, and time which are related to its speed and are not noticeable except at speeds approaching that of light

b

: an extension of relativity theory to include gravity and its related acceleration effects