Definition
Quarter turn
A quarter turn rotates something through one quarter of a full circle: 90 degrees.
What it means
Picture an arrow attached to a pin. Swing it around one corner of an invisible square, keeping the pin fixed. A clockwise quarter turn from up points right. An anticlockwise quarter turn from up points left, so the direction of the turn matters.
Remember it
One square corner is one quarter turn; four such turns make a full turn.
Example
A toy robot faces north. It makes one quarter turn clockwise. Clockwise from north is east, so the robot now faces east. The turn measured 90°.
Watch for
When the finishing direction matters, a quarter turn must say or show clockwise or anticlockwise. The two choices do not end in the same place.
Common mix-up
A quarter turn is 90°, not 45°. Four quarter turns, not eight, make one full turn.
Exact meaning
A quarter turn is a rotation of 90° about a fixed centre. It changes a direction to a perpendicular direction; clockwise and anticlockwise quarter turns finish in different directions.