no
An irregular pentagon.
An irregular octagon.
an four sided figure is called a quadrilateral.
It can be irregular too so it's a septagon
no
An irregular polygon
An irregular pentagon.
An irregular octagon.
A trapezium.
an four sided figure is called a quadrilateral.
It can be irregular too so it's a septagon
Add up the lengths of the sides.
Not exactly. They are two names for the same shape. The typical shape consists of a four-sides figure with opposite sides (and angles) equal. Each pair of parallel sides are the same length.
A quadrilateral can have uneven four sides
Decagon(10 sides polygon).
It can be a quadrilateral, though quadrilaterals are 4-sided shapes in general.