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
sound
Percussion 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
- Statistics
- Tables, graphs & diagrams
- Terms for numbers

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