Question: symbol which indicates the relationship between two values

title: List of mathematical symbols
text: = : : = ≡ : ⇔ ≜ ≝ ≐ = : ( \ displaystyle = : ) : = ( \ displaystyle : = ) ≡ ( \ displaystyle \ equiv ) \ equiv : ⇔ ( \ displaystyle : \ Leftrightarrow ) : \ Leftrightarrow ≜ ( \ displaystyle \ triangleq ) \ triangleq = d e f ( \ displaystyle ( \ overset ( \ underset ( \ mathrm ( def ) ) ( ) ) ( = ) ) ) \ overset ( \ underset ( \ mathrm ( def ) ) ( ) ) ( = ) ≐ ( \ displaystyle \ doteq ) \ doteq definition is defined as ; is equal by definition to everywhere x : = y , y = : x or x ≡ y means x is defined to be another name for y , under certain assumptions taken in context . ( Some writers use ≡ to mean congruence ) . P ⇔ Q means P is defined to be logically equivalent to Q . cosh ⁡ x : = e x + e − x 2 ( \ displaystyle \ cosh x : = ( \ frac ( e ^ ( x ) + e ^ ( - x ) ) ( 2 ) ) ) ( a , b ) : = a ⋅ b − b ⋅ a ( \ displaystyle ( a , b ) : = a \ cdot b-b \ cdot a )