true

Etymology

From Middle English trewe, from Old English trīewe, (Mercian) trēowe (“trusty, faithful”), from Proto-Germanic *triwwiz (compare Saterland Frisian trjou (“honest”), Dutch getrouw and trouw, German treu, Norwegian and Swedish trygg (“safe, secure’”), from pre-Germanic *drewh₂yos, from Proto-Indo-European *drewh₂- (“steady, firm”) (compare Irish dearbh (“sure”), Old Prussian druwis (“faith”), Ancient Greek δροόν (droón, “firm”)), extension of *dóru (“tree”). More at tree. For the semantic development, compare Latin robustus (“tough”) from robur (“red oak”).

adj

1. (of a statement) Conforming to the actual state of reality or fact; factually correct.
   This is a true story.
   Whether modern, industrial man is less or more warlike than his hunter-gatherer ancestors is impossible to determine.[…]One thing that is true, though, is that murder rates have fallen over the centuries, as policing has spread and the routine carrying of weapons has diminished. Modern society may not have done anything about war. But peace is a lot more peaceful. 2013-07-20, “Old soldiers?”, in The Economist, volume 408, number 8845
   1. As an ellipsis of "(while) it is true (that)", used to start a sentence
      True, I have only read part of the book, but I like it so far.
2. Conforming to a rule or pattern; exact; accurate.
   a true copy; a true likeness of the original
3. (logic) Of the state in Boolean logic that indicates an affirmative or positive result.
   "A and B" is true if and only if "A" is true and "B" is true.
4. Loyal, faithful.
   He’s turned out to be a true friend.
5. Genuine; legitimate, valid.
   This is true Parmesan cheese.
   The true king has returned!
   The Harpe. […] A harper with his wreſt maye tune the harpe wrong / Mys tunyng of an Inſtrument ſhal hurt a true ſonge 1568, William Cornysh, “In the Fleete Made by Me William Cornishe …”, in John Skelton, edited by J[ohn] S[tow], Pithy Pleasaunt and Profitable Workes of Maister Skelton, Poete Laureate, Imprinted at London: In Fletestreate, neare vnto Saint Dunstones Churche by Thomas Marshe, →OCLC; republished as Pithy Pleasaunt and Profitable Workes of Maister Skelton, Poete Laureate to King Henry the VIIIth, London: Printed for C. Davis in Pater-noster Row, 1736, →OCLC, page 290
   The Washington Monument is often described as an obelisk, and sometimes even as a “true obelisk,” even though it is not. A true obelisk is a monolith, a pylon formed out of a single piece of stone. 2012-01, Henry Petroski, “The Washington Monument”, in American Scientist, volume 100, number 1, page 16
6. Used in the designation of group of species, or sometimes a single species, to indicate that it belongs to the clade its common name (which may be more broadly scoped in common speech) is restricted to in technical speech, or to distinguish it from a similar species, the latter of which may be called false.
   true sparrows (Passer)
   true spiders
   true blusher (Amanita rubescens, as distinguished from the false blusher, Amanita pantherina)
7. (of an aim or missile in archery, shooting, golf, etc.) Accurate; following a path toward the target.
   Whate'er the weapon, still his aim was true, Nor e'er in vain the fatal bullet flew. 1801, Mrs. Cowley, “The siege of Acre”, in The British Critic, volumes 17-18, page 521
   I held my breath and struck the ball. My aim was true, but I didn't give the damn thing enough gas. It died three feet from the cup. 2008, Carl Hiaasen, The downhill lie: a hacker's return to a ruinous sport, page 188
8. (of a mechanical part) Correctly aligned or calibrated, without deviation.
   Is my bike wheel true? It feels unsteady.
9. (chiefly probability) Fair, unbiased, not loaded.
   Let Z_t be twice the value of a true die shown on the t-th toss. 1990, William W. S. Wei, Time Series Analysis, page 8
   In fact, few profit margins can be predicted with such reliability as those provided by a true roulette wheel or other game of chance. 2006, Judith A. Baer, Leslie Friedman Goldstein, The Constitutional and Legal Rights of Women: Cases in Law and Social Change
   We do not reject, because 9 heads and 3 tails is in a set of reasonably likely results when we toss a true coin. 2012, Peter Sprent, Applied Nonparametric Statistical Methods, Springer Science & Business Media, page 5
10. (of a literary genre) based on actual historical events.
    true crime true romance
    [A] skinny blonde of about twenty sitting in an armchair by an electric fire reading a true romance magazine. 1965, James Holledge, What Makes a Call Girl?, London: Horwitz Publications, page 69

adv

1. (of shooting, throwing etc) Accurately.
   This gun shoots true.
   Plant breeding is always a numbers game.[…]The wild species we use are rich in genetic variation, and individual plants are highly heterozygous and do not breed true. In addition, we are looking for rare alleles, so the more plants we try, the better. 2013 May-June, David Van Tassel, Lee DeHaan, “Wild Plants to the Rescue”, in American Scientist, volume 101, number 3
2. (archaic) Truthfully.

noun

1. (uncountable) The state of being in alignment.
   Some toolmakers are very careless when drilling the first hole through work that is to be bored, claiming that if the drilled hole comes out of true somewhat it can be brought true with the boring tool. 1904, Lester Gray French, Machinery, volume 10
   The crate shifted on its pallet, out of sync now. As the lift withdrew, the crate skidded with it, dragged by friction and gravity, skewing farther and farther from true. 1988, Lois McMaster Bujold, Falling Free, Baen Publishing,, page 96
   The strength and number of blows depends on how far out of true the shafts are. 1994, Bruce Palmer, How to Restore Your Harley-Davidson
2. (uncountable, obsolete) Truth.
3. (countable, obsolete) A pledge or truce.

verb

1. To straighten (of something that is supposed to be straight).
   He trued the spokes of the bicycle wheel.
2. To make even, level, symmetrical, or accurate, align; adjust.
   We spent all night truing up the report.