Prefix · quantity · four
Means "four": quadrant, quadruple, quadrilateral, quadruped, quadruplets, quadriceps.
Written by Bryan López, English teacher · Updated
Quad-/quadr- comes from Latin "quattuor" (four) and signals that something has four parts, sides, or multiples: quadrant = one quarter of a circle (four of them make the whole); quadruple = four times as much; quadrilateral = a shape with four sides; quadruped = an animal that walks on four legs; quadriceps = the four-headed muscle in the thigh; quadruplets = four babies born in the same birth.
Both quad- (Latin) and tetra- (Greek) mean "four," but they are not interchangeable: words of Latin origin use quad- (quadrant, quadruped, quadruple, quadrilateral); words of Greek origin use tetra- (tetrahedron, tetrachloride, tetrapod). The word's historical root determines the prefix. "Quadrahedron" and "tetrangle" do not exist.
Attaches to nouns to indicate "four" or "fourfold":
Pronunciation: /kwɒd/. The variant "quadr-" appears before vowels: quadrilateral, quadrangle. Spanish cognates: quadrant/cuadrante, quadruple/cuádruple, quadrilateral/cuadrilátero, quadruped/cuadrúpedo, quadriceps/cuádriceps. Latin equivalent of Greek tetra-.
quad-/quadr-/kwɒd/
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Both mean "four" but come from different languages. Words of Latin origin take quad-; words of Greek origin take tetra-. "Quadrahedron" and "tetrangle" are not words. The number prefix pattern in English follows the root language: Latin words use uni-(1), bi-(2), tri-(3), quad-(4); Greek words use mono-(1), di-(2), tri-(3), tetra-(4).
A trick to remember it
Quad- = four. Spanish cognates: quadrant/cuadrante, quadruple/cuádruple, quadrilateral/cuadrilátero, quadruped/cuadrúpedo. It is the Latin equivalent of Greek tetra-. Number sequence: uni-(1), bi-(2), tri-(3), quad-(4), penta-(5), hexa-(6), hepta-(7), octa-(8).
Exercise 1 · Form the word
Exercise 2 · Pick the right one
What is the difference between "quad-" and "tetra-"?
The prefix quad-/quadr- means "four": quadrant, quadruple, quadrilateral, quadruped, quadruplets, quadriceps. In Spanish it usually maps to cuadr-/cuat-.
The prefix quad-/quadr- is pronounced /kwɒd/. For example, "quadrant".
"rant" becomes "quadrant". It is a typical example of the quad-/quadr- prefix.
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