An angle is two rays that share a common endpoint. Angles are classified into groups according to their measure by degrees:

Acute Angle

• An acute angle has an angle measure greater than 0 and less than 90 degrees
  

Right Angle

• A right angle has an angle measure equal to 90 degrees

Obtuse Angle

• An obtuse angle has an angle measure greater than 90 and less than 180 degrees

Straight Angle

• A straight angle has an angle measure equal to 180 degree