It is derived from two Greek words geo (earth) and metrein (measure). Thus geometry is the study or measure of earthly objects.

It is a set of structures that is composed of undefined terms, defined terms, axioms or postulates, and theorems.

He is the father of Geometry.

It is a closed figure composed of line segments.

A polygon with three sides.

These are statements which is accepted and assumed as true without proof that can be used as reasons in proving some mathematical statements.

It is an angle between to sides of a triangle

It is a part of a line between two points and including the endpoints.

These are statements that can be derived from axioms, definitions, and previously proven theorems using deductive reasoning.

These are propositions that follow immediately from a theorem just established.