noun

acute angle

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Acute angle (noun) means an angle that measures more than 0 degrees and less than 90 degrees. Example: “Each corner of an equilateral triangle is an acute angle of 60 degrees.”

noun

An angle that measures more than 0 degrees and less than 90 degrees.

"Each corner of an equilateral triangle is an acute angle of 60 degrees."

"Measure the acute angle between the two lines with a protractor."

How to use acute angle

Learner’s notes

In plain EnglishAn angle narrower than the corner of a square.

When to use it

Neutral. A standard maths term taught from primary school onwards.

Memory tip

Acute means sharp — think of a sharp point or an acute pain. A sharp angle is a small one.

Trace the full origin ↓

Easily confused with

acute angle / obtuse angle acute angle / right angle

Common pairings

acute angle triangle measure an acute angle acute and obtuse angles

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Fill the gap

Can you complete this real example?

Each corner of an equilateral triangle is an _____ of 60 degrees.

Etymology

From Latin acutus 'sharpened, pointed', past participle of acuere 'to sharpen'.

Origin: Latin

Antonyms

obtuse angle right angle reflex angle

Rhymes for acute angle

angle tangle mangle bangle dangle jangle wrangle triangle untangle strangle rectangle

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Frequently asked questions

What is the difference between an acute angle and an obtuse angle?

An acute angle is smaller than 90 degrees, so it looks sharp and narrow. An obtuse angle is greater than 90 degrees but less than 180, so it looks wide and open. A 90-degree angle itself is neither — it is a right angle.

Can a triangle have more than one acute angle?

Yes, and it must have at least two. Because the three angles add to 180 degrees, a triangle can have at most one right or obtuse angle. When all three are under 90 degrees it is called an acute triangle.

Is 90 degrees an acute angle?

No. Acute means strictly less than 90 degrees. Exactly 90 degrees is a right angle, usually marked with a small square rather than an arc.

What is the meaning of acute angle?

"acute angle" (noun) means an angle that measures more than 0 degrees and less than 90 degrees.