Aletheia or Alethia (/ælɪˈθaɪ.ə/;[1] Ancient Greek: ἀλήθεια) is truth or disclosure in philosophy. Originating in Ancient Greek philosophy, the term was explicitly used for the first time in the history of philosophy by Parmenides in his poem On Nature, in which he contrasts it with doxa.
It was revived in the works of 20th-century philosopher Martin Heidegger. Although often translated as "truth", Heidegger argued that it is distinct from common conceptions of truth.