Answer:
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Definition: 1 Mark
Explanation: 1 Mark
Example: 1 Mark

A quadrilateral is a type of polygon. It has four sides.
Quadrilateral means "four sides"(quadmeans four,lateralmeans side).
It is a 2-dimensionalclosedshape and hasstraightsides.
In the quadrilateral, ABCD, here (AB, BC), (BC, CD), (CD, DA) and (DA, AB) are the adjacent side whereas (AB, CD) and (AD, BC) are the opposite sides.
The four angles are $\angle$ABC,$\angle$BCD,$\angle$CDA,$\angle$DAB.