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

With space and time so intimately linked in relativity, any account of how space emerges must also explain time. —Adam Becker, Scientific American, 1 Feb. 2022

This is reflected in the idea of linguistic relativity. —Elpida Kokkota, Forbes, 4 Sep. 2024

The challenge for theorists is to find ways to unite the disparate theories of relativity and quantum mechanics in a theory of ‘loop’ quantum gravity that correctly predicts observations. —The Physics Arxiv Blog, Discover Magazine, 31 July 2024

Because of effects explained by Albert Einstein’s theory of relativity, clocks tick ever-so-slightly faster on the Moon than on Earth, posing difficulties for communication and navigation. —Byhannah Richter, science.org, 14 Aug. 2024

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

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