0Types of Triangles by Length
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In an equilateral triangle, all three sides are the same length. An equilateral triangle is always equiangular (see below).
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In an isosceles triangle, two sides are the same length. An isosceles triangle may be right, obtuse, or acute (see below).
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In a scalene triangle, none of the sides are the same length. A scalene triangle may be right, obtuse, or acute (see below).
Types of Triangle by Angle
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In an equiangular triangle, all the angles are equal—each one measures 60 degrees. An equiangular triangle is a kind of acute triangle, and is always equilateral.
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In a right triangle, one of the angles is a right angle—an angle of 90 degrees. A right triangle may be isosceles or scalene.
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In an obtuse triangle, one angle is greater than a right angle—it is more than 90 degrees. An obtuse triangle may be isosceles or scalene.
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In an acute triangle, all angles are less than right angles—each one is less than 90 degrees. An acute triangle may be equilateral, isosceles, or scalene.
