An acute angle is an angle measuring between 0 and 90 degrees.

Example:

The following angles are all acute angles.

An obtuse angle is an angle measuring between 90 and 180 degrees.

Example:

The following angles are all obtuse.

A right angle is an angle measuring 90 degrees. Two lines or line segments that meet at a right angle are said to be perpendicular. Note that any two right angles are supplementary angles (a right angle is its own angle supplement).

Example:

The following angles are both right angles.