quadri-

from The Century Dictionary.

• 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-.

from the GNU version of the Collaborative International Dictionary of English.

• A combining form meaning four, four times, fourfold.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• prefix Four.