Quick Summary

The English prefix tri-, derived from both Greek and Latin, means “three.” Some common English vocabulary words that contain this prefix include triathlon, trio, and triangle. You can easily remember that the prefix tri- means “three” via the word tricycle, which is a bicycle with “three” wheels instead of two that promotes stability for young riders.

Triple Threat

The English prefix tri-, derived from both Latin and Greek roots, means “three.” Let’s do a “triple double” by looking at these two root words that mean “three!”

Math, as one might expect, often uses number prefixes, and the prefix tri- meaning “three” is no exception. A triangle is a figure with “three” angles. The branch of mathematics which primarily studies triangles is trigonometry, or the measurement of figures containing “three” angles. The number trillion, bandied about so much these days in the news, is the number 1000 times itself another “three” times. If you triple a trillion, you make it “three” times bigger!

The Ironman triathlon consists of “three” grueling athletic contests: 2.4 miles of swimming, 112 miles of cycling, and a full marathon distance for running. Athletes participating in the Ironman could not do well without their triceps, or that muscle which attaches in “three” places on the back of the upper arm, opposite the biceps. Rest assured that these elite triathletes do not use tricycles, or a bicycle with “three” wheels, in the cycling part of the contest!

The humanities as well love using the prefix tri-, or “three.” A trio is a musical group that consists of “three” singers. A triad can also refer to any group of “three.” The god Poseidon wielded the powerful trident, or mighty spear that had “three” prongs. A trilogy consists of a series of “three” books, such as in the series The Lord of the Rings.

And last but not least, a dilemma perhaps doesn’t seem so bad when you have a trilemma on your hands instead, or a very difficult choice between “three” options instead of just two!

Now you will no longer have to “try” to figure out what the English prefix tri- means, perhaps tripling your time saved by not having to look in the dictionary for all those once “trying” tri- words!

  1. triangle: geometrical figure with ‘3’ angles
  2. trigonometry: the mathematical study of figure with ‘3’ angles
  3. trillion: the number 1000 multiplied by itself another ‘3’ times
  4. triple: to multiply by ‘3’
  5. triathlon: an athletic contest featuring ‘3’ primary events
  6. triceps: a muscle with ‘3’ heads, or places where it attaches
  7. tricycle: a bicycle with ‘3’ wheels
  8. trio: a group of ‘3’ singers
  9. triad: any group of ‘3’
  10. trident: a spear with ‘3’ prongs
  11. trilogy: a series which consists of ‘3’ books
  12. trilemma: a choice you have to make between ‘3’ equally viable options


  • trammel

    When you trammel something or someone, you bring about limits to freedom or hinder movements or activities in some fashion.

  • triptych

    A triptych is a painting or carving made of three related panels hinged together in such a way that the two side panels can be folded over the central one.

  • travail

    You refer to a situation or work as travail if it's very tiring, very unpleasant, or very difficult.

  • trivial

    Something trivial is of little value or is not important.

  • triad

    the cardinal number that is the sum of one and one and one

  • triangle

    a three-sided polygon

  • triathlete

    one who competes in three different sports, usually running, biking, and swimming

  • triathlon

    a contest during which athletes score points in three different sports

  • triceps

    any skeletal muscle having three origins (but especially the triceps brachii)

  • tricolor

    having or involving three colors

  • tricycle

    a vehicle with three wheels that is moved by foot pedals

  • trident

    a spear with three prongs

  • trigonometry

    the mathematics of triangles and trigonometric functions

  • trilateral

    involving three parties

  • trilingual

    using or knowing three languages

  • trillion

    one quintillion in Great Britain

  • trilobite

    an extinct arthropod that was abundant in Paleozoic times

  • trilogy

    a set of three literary or dramatic works related in subject or theme

  • trio

    the cardinal number that is the sum of one and one and one

  • triple

    increase threefold

  • triplet

    the cardinal number that is the sum of one and one and one

  • tripod

    a three-legged rack used for support

  • trivia

    something of small importance

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