Symbols in Geometry

Common Symbols Used in Geometry

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

Symbol Meaning Example In Words
triangle symbol Triangle triangleABC has 3 equal sides Triangle ABC has three equal sides
angle symbol Angle angleABC is 45° The angle formed by ABC is 45 degrees.
perpendicular Perpendicular ABperpendicularCD The line AB is perpendicular to line CD
parallel Parallel EFparallelGH The line EF is parallel to line GH
degrees Degrees 360° 360 degrees (a full rotation!)
right angle symbol Right Angle (90°) right angle is 90° A right angle is 90 degrees
line segment AB Line Segment "AB" AB The line segment between A and B
line AB Line "AB" line AB The infinite line that includes A and B
ray AB Ray "AB" ray AB The line that starts at A, goes through B and continues on
congruent Congruent (same shape and size) triangleABC congruent symbol triangleDEF
Triangle ABC is congruent to triangle DEF
similar Similar (same shape, different size) symbol triangleDEFsimilarsymbol triangleMNO Triangle DEF is similar to triangle MNO
therefore symbol Therefore a=b therefore b=a a 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.