Geometry usually begins with the point, the line and the plane. Later on, space is also added.
The point is a dimensionless location in one or more dimensions. A point can also be said to have zero dimension.
When two points are separated by a distance, they can be connected by a line. The line has one dimension and can extend past either of the two points.
If the line stays between the two points, is called a closed line segment. The points are now called end points.
Otherwise, if the line extends past one point or the other but not both, then it is an open line segment. An open line segment is also called a ray. In higher math, it is also referred to as a vector.
A plane is a geometric structure that can be defined by three points or two lines.
The plane contains all the points or lines that define it. It can also extend in all directions. A plane has two dimensions.
When two lines cross in a plane, they are intersecting lines. If they don't cross and they are in the same plane, then they are parallel.
In geometry, an angle is the amount of bend between two lines or line segments that intersect in the same plane.
In order to measure an angle, a circle, which is a two-dimensional shape in a plane, is divided into 360 pieces called degrees.
An acute angle is less than 90 degrees.
An obtuse angle is greater than 90.
A right angle is exactly 90.
A right angle is also symbolized by:
