A triangle is a flat shape with three sides and three angles, like a slice of pizza, a yield sign, or the Greek letter Delta. If you look carefully, you'll notice triangles all around you!

A triangle is a polygon, which is a closed shape like a square or a hexagon, but a triangle has only three sides. Wedges of pie and some tortilla chips are shaped like triangles. If you invite your crush to a movie and they bring a date, you have yourself a love triangle. Triangle comes from the Latin word triangulus, "three-cornered" or "having three angles," from the roots tri-, "three," and angulus, "angle or corner."

Definitions of triangle

n a three-sided polygon

trigon, trilateral
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acute triangle, acute-angled triangle
a triangle whose interior angles are all acute
equiangular triangle, equilateral triangle
a three-sided regular polygon
isosceles triangle
a triangle with two equal sides
oblique triangle
a triangle that contains no right angle
obtuse triangle, obtuse-angled triangle
a triangle that contains an obtuse interior angle
right triangle, right-angled triangle
a triangle with one right angle
scalene triangle
a triangle with no two sides of equal length
cuneus, wedge, wedge shape
any shape that is triangular in cross section
an object shaped like an equilateral triangle
Type of:
polygon, polygonal shape
a closed plane figure bounded by straight sides

n something approximating the shape of a triangle

“the coastline of Chile and Argentina and Brazil forms two legs of a triangle
Type of:
form, shape
the spatial arrangement of something as distinct from its substance

n any of various triangular drafting instruments used to draw straight lines at specified angles

Type of:
drafting instrument
an instrument used by a draftsman in making drawings

n a percussion instrument consisting of a metal bar bent in the shape of an open triangle

Type of:
percussion instrument, percussive instrument
a musical instrument in which the sound is produced by one object striking another

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