# Symbols in Geometry

## Common Symbols Used in Geometry

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

SymbolMeaningExampleIn Words
TriangleABC has 3 equal sidesTriangle ABC has three equal sides
AngleABC is 45° The angle formed by ABC is 45 degrees.
PerpendicularABCD The line AB is perpendicular to line CD
ParallelEFGH The line EF is parallel to line GH
Degrees360°360 degrees (a full rotation!)
Right Angle (90°) is 90°A right angle is 90 degrees
Line Segment "AB"AB The line segment between A and B
Line "AB"The infinite line that includes A and B
Ray "AB"The line that starts at A, goes through B and continues on
Congruent (same shape and size)ABC DEF
Triangle ABC is congruent to triangle DEF
Similar (same shape, different size)DEFMNO Triangle DEF is similar to triangle MNO
Thereforea=b b=aa equals b, therefore b equals a

### Example: In ABC, BAC is

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

### Naming Angles

For angles the central letter is where the angle is.

### Example: ABC is 45°

The point "B" is where the angle is.