In a quadrilateral, define each of the following:
(i) Sides                 
(ii)  Vertices               
(iii)  Angles
(iv)Diagonals                    
(v)      Adjacent angles
(vi)Opposite Sides            
(vii)   Opposite sides
(viii)Opposite angles           
(ix)  Interior       
(x)  Exterior

Explanation

(i) Sides:
In a quadrilateral, all the sides may have same of different length.
The four line segments AB, BC, CD and DA are called its sides.

(ii) Vertices
Vertices are the angular points where two sides or edges meet.
A, B, C and D are the four vertices in a quadrilateral.

(iii) Angles
Angle is the inclination between two sides of a quadrilateral. i.e. meeting point of two sides is an angle.
ABC, BCA, CDA and DAB are the four angles in a quadrilateral.

(iv) Diagonals
The lines joining two opposite vertices is called the diagonals in a quadrilateral.
BD and AC are the two diagonals.

(v) Adjacent angles
Angles having one common arm onto the sides is called the adjacent angles.
ABC, BCD are adjacent angles in a quadrilateral.

(vi) Adjacent sides
When two sides have common endpoint is termed as adjacent sides.
AB BC, BC CA, CD DA, DA AB are pairs of adjacent sides in a quadrilateral.

(vii) Opposite sides:
Opposite sides when they don’t meet at any point is termed as opposite sides.
AB CD, BC DA are the pairs of opposite sides in a quadrilateral.

(viii) Opposite angles
Two angles, which are not adjacent angles are termed as opposite angles.
A and C, angles B and D are opposite angles in a quadrilateral.

(ix) Interior The part of plane when points are enclosed within the quadrilateral is called as interior.
(x) Exterior
The part of plane when points are not enclosed within the quadrilateral is called as exterior.