tri-

Tri- is a combining form used like a prefix meaning “three.” Tri- is often used in a great variety of both everyday and technical terms.

Tri- ultimately comes from both Greek treîs, tría and Latin trēs, tria, all of which mean “three.”

An example of a word you may have encountered that features tri- is trident, “a three-pronged instrument or weapon.” The word trident comes from Latin tridēns, which uses the equivalent of the form tri- in the language.

The tri- part of the word means “three,” while the -dent part means “tooth.” Trident literally translates to “three teeth” or “three-toothed.”

Tri- also features in common words such as triangle and tricycle. Learn more about the origins of these words at their entries.

What are some words that use the combining form tri-?

• triaxial
• tridimensional 
• tridymite (using the equivalent form of tri- in Greek)
• triethyl
• trifacial
• trifocal
• trifold
• trigram
• trihedral
• trihydrate
• trihydroxy

The following words use the equivalent forms of tri- in Latin or Greek:

• triad
• triarchy
• triceps
• tridactyl
• tridentate
• triduum
• triennial
• trifolium
• triform
• trigamy
• triglyph
• trigone
• trimeter
• triplex
• tripod
• tritoma

What are some other forms that tri- may be commonly confused with?

• tetr-
• tor-
• tricho-
• trinitro-
• tris-
• -trix
• twi-

Not every word that begins with the letters tri- is necessarily using the combining form tri- to denote “three.” Learn why triage literally means “sorting” at our entry for the word.

Tripods are stands used for holding cameras and telescopes in place. The combining form -pod refers to  “foot.” With this in mind, what does tripod literally mean?