truth

Etymology

From Middle English trouthe, truthe, trewthe, treowthe, from Old English trēowþ, trīewþ (“truth, veracity, faith, fidelity, loyalty, honour, pledge, covenant”), from Proto-Germanic *triwwiþō (“promise, covenant, contract”), from Proto-Indo-European *drū- (“tree”), from Proto-Indo-European *deru- (“firm, solid”), equivalent to true + -th. Cognate with Norwegian trygd (“trustworthiness, security, insurance”), Icelandic tryggð (“loyalty, fidelity”).

noun

1. True facts, genuine depiction or statements of reality.
   The truth is that our leaders knew a lot more than they were letting on.
   The truth depends on, or is only arrived at by, a legitimate deduction from all the facts which are truly material. 1835, Samuel Taylor Coleridge, Henry Nelson Coleridge, quoting Samuel Taylor Coleridge, Specimens of the Table Talk of the late Samuel Taylor Coleridge, volume II, page 19
   The truth is that [Isaac] Newton was very much a product of his time. The colossus of science was not the first king of reason, Keynes wrote after reading Newton’s unpublished manuscripts. Instead “he was the last of the magicians”. 2014-06-21, “Magician’s brain”, in The Economist, volume 411, number 8892, archived from the original on 2018-11-04
2. Conformity to fact or reality; correctness, accuracy.
   There was some truth in his statement that he had no other choice.
   As in much of biology, the most satisfying truths in ecology derive from manipulative experimentation. Tinker with nature and quantify how it responds. 2012-01, Robert M. Pringle, “How to Be Manipulative”, in American Scientist, volume 100, number 1, page 31
3. The state or quality of being true to someone or something.
   Truth to one's own feelings is all-important in life.
4. (archaic) Faithfulness, fidelity.
5. (obsolete) A pledge of loyalty or faith.
6. Conformity to rule; exactness; close correspondence with an example, mood, model, etc.
   The process of grinding is, in fact, regarded as indispensable wherever truth is required, yet that of scraping is calculated to produce a higher degree of truth than has ever been attained by grinding. 1840, Joseph Whitworth, A Paper on Plane Metallic Surfaces or True Planes
7. That which is real, in a deeper sense; spiritual or ‘genuine’ reality.
   The truth is what is.
   Alcoholism and redemption led me finally to truth.
8. (countable) Something acknowledged to be true; a true statement or axiom.
   Hunger and jealousy are just eternal truths of human existence.
9. (physics, dated) Topness; the property of a truth quark.
10. (games) In the game truth or dare, the choice to truthfully answer a question put forth.
    When asked truth or dare, he picked truth.

verb

1. (obsolete, transitive) To assert as true; to declare; to speak truthfully.
   c. 1636 John Ford, The Fancies Chaste and Noble Had they [the ancients] dreamt this, they would have truthed it heaven.
2. To make exact; to correct for inaccuracy.
   A concentrated region of the agricultural test area was intensively ground truthed, not only to identify the crop types, but equally important, also to begin to determine the parameters controlling the radar energy reflected from a crop type at a particular stage of growth. 1974, Proceedings of the International Symposium on Remote Sensing of Environment, page 226
   As is shown in this table, APG images in the validation subset were only truthed with box models, and the 29P images in this subset were never truthed at all. 1990, Advanced Infrared Technology - Part 2, page cxxvi
   This database, which consisists of nearly 180,000 characters, was manually truthed. 2003, Advances in Pattern Recognition ICAPR2003, page 67
3. (nonstandard, intransitive) To tell the truth.
   You keep lying, when you oughta be truthin' 1966, Nancy Sinatra, These Boots Are Made for Walkin'