Something having three parts, units, or members.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "three" in a sentence
"While she browsed the audio books' shelves, I decided to browse the nearby poetry shelves -- all three of them Tsk, Copperfield: I wish you'd game up on your poetry selection overly-weighted on *three* shelves with Rumi, not that there's anything wrong with Rumi of course."
"There were at least three fire engines -- why _three?"
"Chin was eventually subdivided into three statelets: Mahan, Chinhan, and Pynhan (known collectively as Samhan or the three Hans)."