A mathematical constant is a significant value that mathematecians have assigned a symbol representation.

The circle constant τ (tau) is a geometric constant approximately equal to 6.283. The numeric value is defined as the length of any circle's circumference divided by the length of its radius.

The greek letter π (pi) is a geometric constant approximately equal to 3.1456. The numeric value is equal to the length of any circle's circumference divided by its diameter.

Euler's number is a naturally occurring number related to exponential growth and exponential decay.

The golden ratio is a number represented by the greek letter ϕ (phi). The value of ϕ is approximately 1.618 and is a naturally occurring number in nature.

The letter "i" is used in mathematics to represent the square root of negative one. The letter is also used to denote the complex part of a complex number.