A straight angle is an angle equal to 
radians.
Two right angles make a straight angle, and two straight angles make a full angle.
Straight Angle
See also
Acute Angle, Angle, Digon, Full Angle, Obtuse Angle, Reflex Angle, Right AngleExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Straight Angle." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/StraightAngle.html