tri-, tre-

(Greek > Latin: a numerical prefix meaning, three, thrice, threefold; triple; a word element for number 3)

ternary
1. Consisting of, or involving, three; threefold; triple.
2. Third in order or rank.
3. Based on the number three.
4. Pertaining to, consisting of, compounded of, or characterized by a set (or sets) of three; threefold, triple.

A ternary system (of classification), one in which each division is into three parts.

treble
trebly
triacid
Containing three different acid radicals in the molecule.
triact, triactinal, triactine
Having three rays; said of a sponge-spicule.
triad
1. A group or set of three (persons, things, words, attributes, etc.); three collectively or in connexion.
2. Applied to the Trinity.
3. A group of three associated or correlated deities, beings, or powers.
4. A set of three things; especially, in geometry, of three points.
5. A union or conjunction of three; a group or class of three closely associated persons or things.
triadelphous
In biology, a reference to stamens that are united by their filaments into three bundles; of a plant having the stamens so united.
triage (tree AHZH)
The screening and classification of wounded, sick, or injured patients during war or another disaster to determine priority needs and thereby ensure the most efficient use of medical and surgical manpower, equipment, and facilities.

This word is here only because it should be known that it has no etymological connection with the Greek-Latin element tri, “three”.

Triage is a borrowing from Old French trier to "pick, sift, cull" and then from French triage, "a picking out, sorting" then to an act of "sorting according to kind and quality". In World War I, triage was adopted as a military term for the sorting of wounded soldiers into three groups according to the urgency of their injuries on the basis of urgency, chance for survival, etc. By 1974, this usage was extended to refer to any system of allocating limited resources according to urgency or expediency, as in the distribution of food during a famine.

Triage now refers to the screening and classification of wounded, sick, or injured patients during war or any other big disaster to determine priority needs and thereby to ensure the most efficient use of medical and surgical manpower, equipment, and facilities.

The separation of a large number of casualties, in military or civilian disaster medical care, is usually done into three groups:

  1. Those who cannot be expected to survive even with treatment.
  2. Those who will recover without treatment.
  3. The highest priority group, those who will not survive without treatment.

“Triage” was often heard on the radio during the first few days following the destruction of the Twin Towers of the World Trade Center in New York on Tuesday, September 11, 2001; as well as the disaster of Hurricane Katrina after it pounded parts of Louisiana and Mississippi on Monday, August 29, 2005, propelling high winds and sheets of rain that not only endangered lives and property in the Gulf Coast region, but also threatened the United States and its trading partners with widespread economic disruption.

trialogue
A colloquy (a conversation, especially a formal one) among three people.
triandrous, triandric
In botany, having three stamens.
triangle (try-AN-guhl) (s) (noun), triangles (pl)
A figure or object that has three corners and three sides: Maxwell's mother was cutting the sandwiches for her guests into triangles.
triangular (try-ANG-you-luhr) (adjective), more triangular, most triangular
Involving three parties or elements having three aspects: There was a triangular mother-father-child relationship in little Joe's family.
triangularis (try-ANG-you-LAHR-iss) (s) (noun), triangulares (pl)
A facial muscle associated with frowning: For some unexplainable reason, Jackson lost his ability to show his disapproval with any facial expressions because his triangularis would not let his face function in a normal way.
triangulate (try-ANG-you-late) (verb), triangulates; triangulated; triangulating
1. To measure by using trigonometry: Using knowledge of his high school math, Harry was able to triangulate the mountain and determine the height of the cliff he was considering climbing up to.
2. To determine a distance or location by measuring the distance between two points whose exact locations are known and then measuring the intersection between each point and a third unknown point: The map makers were triangulating the countryside so the firemen could locate the precise locations of many homes and other large buildings more precisely.
triangulation (try-ANG-you-lay-shun) (s) (noun), triangulations (pl)
The tracing and measurement of a series or network of triple geometric configurations in order to survey and map out a territory or region: Triangulation today is used for many purposes, including surveying, navigation, metrology, astrometry, binocular vision, and even model rocketry.

Cross references of word families that are related, partially or totally, to: "three, third": terce-; terti-; trigono-; trito-.