theory of relativity; relativistic physics. Developed by Albert Einstein in the early 20th century, it changed the understanding of space, time, and gravity, forming the basis of modern physics. It includes both 狭义相对论 xiá​yì​xiāng​duì​lùn and 广义相对论 guǎng​yì​xiāng​duì​lùn.

Suffix used after verbs or adjectives to form nouns expressing a state, quality, or scope, similar to English "-ity", "-ness", or "-ism".