4
A four-sided plane figure is a quadrilateral or quadrangle, sometimes also called a tetragon. It can be further classified as a rectangle or oblong, kite, rhombus, and square.
Idiom on all fours (Definition of four from the Cambridge Advanced Learner''s Dictionary & Thesaurus © Cambridge University Press)
FOUR definition: a cardinal number, three plus one. See examples of four used in a sentence.
something representing, represented by, or consisting of four units, such as a playing card with four symbols on it
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