Polygon– Simple closed figures having three or more line segment are called polygon (or simple closed curve).

Triangle– A three sided polygon is called triangle.
Quadrilateral– A four sided polygon is called quadrilateral.
Pentagon– A five sided polygon is called a pentagon.
Hexagon– A six sided polygon is called hexagon.
Heptagon– A seven sided polygon is called heptagon.

Octagon– A eight sided polygon is called octagon.
Nonagon– A nine sided polygon is called nonagon.
Decogon– A ten sided polygon is called decogon.
Regular polygon– It’s all side are equal & all angles are also equal then it is called a regular polygon.
Angle– An angle is a figure formed by two rays with the common initial point. The common initial point is called the vertex of the angle & the rays forming the angle are called its arm.
An angle can also be describe by rotating a ray.
Where OA is initial position and it rotate at center O to final position OB.
Then AOB is an angle, O is vertex and OA and OB are sides of angle.

Right angle– If the initial position of a ray is horizontal & it rotates to occupy vertical position then the angle formed is called a right angles(90^0).

Straight angle– If the initial & the final position of a rotating ray are opposite to each other the angle formed is called a straight angle.
Complete angle– If a rotating ray after a complete revolution considers with the initial position the angle formed is called a complete angle.
Adjacent angle– Two angles are said to be adjacent, if they have a common vertex, arm and other two arms are on the opposite side of the common arm.


Kinds of angle:-

Acute angle– An angle whose measure is greater than but less than 90^0 .
Obtuse angle-An angle which is greater than a right angle. But less than straight angle (180^0 ) is called obtuse angle.
Reflex angle– An angle whose measure is more than 1800 but less than 360^0 , is called reflex angle.
Right angle– An angle whose measure is 90^0 .