noun

protractor

pruh-TRAK-ter/prəˈtræktər/

An instrument for measuring and drawing angles.

The protractor lies over two drawn rays to measure their angle.

A transparent semicircular protractor laid over two drawn rays on paper, essential functional degree numerals only 0,90,180; no explanatory writing.

Etymology

proLatinforward

+tractLatinto draw, pull

+orLatinone or something that acts

The pieces describe someone or something that “draws forward.” The word first named someone who lengthens an action, and later became the name of an instrument for measuring and drawing angles.

In context

mathantics6:49

Then you make sure that one of the rays lines up with the straight line on the protractor.

Math Antics - Angles & Degrees

More examples

Place the protractor's center mark at the corner of the angle.
My protractor shows that this angle measures 60 degrees.
The students share two protractors during geometry class.

Forms

protractor · protractors

Similar words

goniometer: Measures angles, often in specialized scientific or medical settings.
angle finder: Typically measures angles between physical surfaces rather than on paper.