1. Definition

2. Practise

B2 a flat shape with three straight sides: an equilateral/isosceles triangleGeometrical shapesSpherical, circular and annular objects › anything that has three straight sides: Which earrings did you buy in the end - the triangles or the circles?Geometrical shapesSpherical, circular and annular objects › a musical instrument consisting of a thin metal bar bent into a triangle shape that is hit with a metal bar to make a soundPercussion instruments › US for set squareGeometrical and mathematical instruments › (also frame) a three-sided frame for arranging the balls at the start of a game of billiards, pool, etc.Snooker, pool and billiards

(Definition of triangle noun from the Cambridge Advanced Learner's Dictionary & Thesaurus
© Cambridge University Press)

Focus on the pronunciation of triangle
You are looking at an entry to do with Geometrical & mathematical instruments, but you might be interested in these topics from the **Mathematics & arithmetic** topic area:

- Addition, subtraction, multiplication & division
- Averages
- Branches & types of mathematics
- Calculations & calculating
- Fractions
- Geometrical shapes
- Geometry: bends, loops & curves
- Geometry: describing angles, lines & orientations
- Geometry: parts of geometrical shapes
- Geometry: properties of circles & curves
- Mathematical symbols
- Numbering & counting
- Numbers generally
- Numbers: cardinal, including nought & zero
- Numbers: groups of things according to number
- Numbers: ordinal
- Numbers: single, double & multiple
- Numerical relationships
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- Terms for numbers

“triangle”: synonyms and related words:

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to direct the way that a ship, aircraft, etc. will travel, or to find a direction across, along, or over an area of water or land, often by using a map

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