Individual angles There is some common terminology for angles, whose measure is always non-negative (see '): An angle equal to 0° or not turned is called a zero angle. An angle smaller than a right angle (less than 90°) is called an acute angle ("acute" meaning "sharp"). An angle equal to turn (90° or radians) is called a right angle. Two lines that form a right angle are said to be normal, orthogonal, or perpendicular. An angle larger than a right angle and smaller than a straight angle (between 90° and 180°) is called an obtuse angle ("obtuse" meaning "blunt"). An angle equal to turn (180° or radians) is called a straight angle. An angle larger than a straight angle but less than 1 turn (between 180° and 360°) is called a reflex angle. An angle equal to 1 turn (360° or 2 radians) is called a full angle, complete angle, round angle or perigon. An angle that is not a multiple of a right angle is called an oblique angle.
Individual angles There is some common terminology for angles, whose measure is always non-negative (see '): An angle equal to 0° or not turned is called a zero angle. An angle smaller than a right angle (less than 90°) is called an acute angle ("acute" meaning "sharp") An angle equal to turn (90° or radians) is called a right angle. Two lines that form a right angle are said to be normal, orthogonal, or perpendicular. An angle larger than a right angle and smaller than a straight angle (between 90° and 180°) is called an obtuse angle ("obtuse" meaning "blunt"). An angle equal to turn (180° or radians) is called a straight angle. An angle larger than a straight angle but less than 1 turn (between 180° and 360°) is called a reflex angle. An angle equal to 1 turn (360° or 2 radians) is called a full angle, complete angle, round angle or perigon. An angle that is not a multiple of a right angle is called an oblique angle.