Symbols in Geometry

Common Symbols Used in Geometry

Symbols save time and space when writing. Here are the most common geometrical symbols:

SymbolMeaningExampleIn Words
triangle symbolTriangletriangleABC has 3 equal sidesTriangle ABC has three equal sides
angle symbolAngleangleABC is 45° The angle formed by ABC is 45 degrees.
perpendicularPerpendicularABperpendicularCD The line AB is perpendicular to line CD
parallelParallelEFparallelGH The line EF is parallel to line GH
degrees Degrees360°360 degrees (a full rotation!)
right angle symbolRight Angle (90°)right angle is 90°A right angle is 90 degrees
line segment ABLine Segment "AB"AB The line segment between A and B
line ABLine "AB"line ABThe infinite line that includes A and B
ray ABRay "AB"ray ABThe line that starts at A, goes through B and continues on
congruentCongruent (same shape and size)triangleABC congruent symbol triangleDEF
Triangle ABC is congruent to triangle DEF
similarSimilar (same shape, different size)symbol triangleDEFsimilarsymbol triangleMNO Triangle DEF is similar to triangle MNO
therefore symbolThereforea=b therefore b=aa equals b, therefore b equals a

Example: In triangleABC, angleBAC is right angle

Is really saying: "In triangle ABC, the angle BAC is a right angle"

angle abc

Naming Angles

For angles the central letter is where the angle is.

Example: angleABC is 45°

The point "B" is where the angle is.