The branch of mathematics that is concerned with measurement, properties and relationship between lines, points, solids and surfaces. Plane geometry and solid geometry are two areas of geometry. Plane geometry is a two dimensional that deals with shapes like circles, triangles and lines.

**Line**

The basic term in the geometry is a line, that extends forever in both the directions and the line segment is that does not extend forever.

**Angle**

The rotation of two intersecting lines on the other is nothing but an angle. The vertex is the common end point and the rays are called the side

**One and two dimensional figures**

A one dimensional figure has only length but no width. A line or ray or segment is the examples of one dimensional figure.

Two dimensional figure is also called as planar figure or simply a plane which has both width and length but no thickness. It is a set of line segments (sides) and curve segments (arcs) lying in a single plane and these sides and arcs are known as edges of the figure. Though the edges are one dimensional, they lie in a plane which is two dimensional.

There are five types of angles in geometry namely zero, acute, right, obtuse and straight angles.

**Zero angle** An angle in which both initial and terminal sides are the same and also whose measure is zero is called zero angle.

**Acute angle** an angle which is less than 900.

**Right angle:** An internal angle which is equal to 900.

**Obtuse angle:**An angle which is more than 900 but less than 1800.

**Straight angle:** An angle which is 1800.

## Parallel and Perpendicular Axis

Lines that never intersect in the same plane are called parallel axis lines and right angle intersections of lines are known as perpendicular axis lines.