What does regular and irregular mean?

Answer 1

A regular polygon (a closed plane figure of straight lines) has all equal angles and all equal side lengths. For example, a square is a regular quadrilateral, because it's four edges are all the same length, and it's angles are all equal (90 degrees). A regular triangle is an equilateral triangle.

An irregular polygon does not have equal sides and angles. N.B to be regular, a polygon must have both equal sides and equal angles. If a polygon has equal sides but unequal angles it is not a regular polygon.