All sides in a regular polygon are of equal length, and the internal angles are equal too, whereas those of an irregular polygon are of varying sizes.

Regular pentagon

A regular pentagon has 5 equal sides and five equal angles totalling 540°.

Irregular pentagon

An irregular pentagon has 5 sides of varying lengths and 5 differently sized angles totalling 540°.

Regular octagon

An octagon has 8 equal sides and 8 equal angles, totalling 1080°.