tri-

1.
a combining form meaning “three,” used in the formation of compound words:
triacid; triatomic.
Origin
Middle English < Latin, combining form representing Latin trēs, tria, Greek treîs, tría three
British Dictionary definitions for tri-

tri-

prefix
1.
three or thrice: triaxial, trigon, trisect
2.
occurring every three: trimonthly
Word Origin
from Latin trēs, Greek treis
Word Origin and History for tri-

word-forming element meaning "three," from Latin tres (neuter tria) or Greek treis (neuter tria) "three" (see three).

tri- in Medicine

tri- pref.

  1. Three: tricuspid.

  2. Containing three atoms, molecules, or groups: triacetic acid.