Symbols in Geometry

Common Symbols Used in Geometry

Symbols save time and space when writing. Here are the most common geometrical symbols (also see Symbols in Algebra):

Symbol	Meaning	Example	In Words
△	Triangle	△ABC has 3 equal sides	Triangle ABC has three equal sides
∠	Angle	∠ABC is 45°	The angle formed by ABC is 45 degrees.
⊥	Perpendicular	AB⊥CD	The line AB is perpendicular to line CD
∥	Parallel	EF∥GH	The line EF is parallel to line GH
°	Degrees	360°	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)	△DEF∼△MNO	Triangle DEF is similar to triangle MNO
∴	Therefore	a=b b=a	a equals b, therefore b equals a

Naming Angles

For angles the central letter is where the angle is.