An Etymological Dictionary of Astronomy and Astrophysics

1. The quality of being true, genuine, actual, or factual.
   

2. Something that is → true as opposed to → false.
   

3. Logic: The correct corresponding of a → proposition with a → fact. See also → truth value, → partial truth.

Etymology (EN): M.E. treuthe; O.E. trêowth “faith, faithfulness, fidelity; quality of being true,” from triewe, treowe “faithful,” → tue, with suffix *-itho-th.

Etymology (PE): Noun from râstin, → true, + noun suffix -i.