Acute angle

⦟ is the acute angle symbol: it names an angle under 90. In geometry notation, its name is more specific than the general angle sign . In right-to-left text, the mark can mirror without changing its meaning.

Text symbol

What ⦟ means

This acute angle symbol names an angle smaller than 90 degrees. An angle is the opening between two lines meeting at a point; an acute one is narrower than a right angle. A door left just ajar gives an everyday picture.

The English phrase “acute angle” has a recorded use from circa 1560.

In right-to-left text, the sign may mirror, so its point can face the other way. The mathematical reading stays the same: an acute angle.

Mathematical and technical; in a formula, it reads as geometry notation.

Don't confuse it with

∠

Angle

⦟ is drawn with three strokes; ∠ has two. If a font makes their outlines look alike, count the strokes.

Questions people ask

Why does ⦟ show as a box on some devices?

Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.