Greek Origin:
* Tripod: (τρíπους - trípous) A three-legged stand.
* Triangle: (τριγωνον - trígōnon) A three-sided polygon.
* Tripartite: (from τριμερής - trimerēs, meaning "three parts") Divided into three parts.
* Trilogy: (from τρία - tríā, meaning "three" and λόγος - lógos, meaning "word" or "speech") A set of three related works (e.g., plays, novels).
Latin Origin (often with similar Greek roots):
* Tribunal: A court of justice; a judge's seat (originally three-seated).
* Tribune: A Roman official who represented the plebeians. (etymology connects to "tribus," tribe)
* Triceps: A muscle with three heads.
* Trident: A three-pronged spear.
* Triennial: Occurring every three years.
* Tricycle: A vehicle with three wheels.
* Trimester: A period of three months.
The prefix "tri-" is incredibly productive, so many more words exist using it in scientific and technical terminology.