from The American Heritage® Dictionary of the English Language, 4th Edition
- Four: quadrilateral.
- Square: quadrate.
from Wiktionary, Creative Commons Attribution/Share-Alike License
from the GNU version of the Collaborative International Dictionary of English
- A combining form meaning four, four times, fourfold.
from The Century Dictionary and Cyclopedia
- An element in many compounds of Latin origin or formation, meaning ‘four.’ In quadrangle, quadrangular (as in Latin), and in quadrennial, quadrennium, it is reduced to quadr-.
Middle English, from Latin; see kwetwer- in Indo-European roots.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin quattuor ("four"). (Wiktionary)