A triangle is a shape with three sides and three angles. The sides of a triangle must be straight lines, and the angles must add up to 180 degrees.
Triangles can be classified by their side lengths and by their angle measures. Side lengths can be equal or unequal, and angle measures can be acute, obtuse, or right.
The triangle has three sides.
Noun:
a closed figure with three straight sides and three angles.
Adjective:
having three sides or angles.
The word "triangle" comes from the Greek word "triagōnon", which means "three-angled".
The first recorded use of the word "triangle" in English was in the 14th century.
The word "triangle" is a Greek word, and it is related to the Latin word "triangulum".
Look around the room. What objects contain triangles?
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