# Constant

## Definition

A symbol which represents a unique quantity in all circumstances is called constant.

Symbols are mainly used to represent the numbers which are constant in all the situations. Actually, the symbols are assumed to be equal to such numbers and express quantities by the symbols everywhere.

For example, $24$ hours is a day. It is constant every year and every day, and it does not change on every factor. Therefore, assume the hours of a day is denoted by a letter $h$ and it is expressed in mathematics as given here.

$h = 24$

Now, just write $h$ instead of $24$ hours wherever you want.

### Examples

Scientists represent some unchangeable numbers by some symbols based on this algebraic concept and some of them are globally recognized by the same symbols to respect their inventions. Here are three understandable examples.

1

#### Neper Constant

John Napier introduced natural logarithmic system by considering an irrational number $2.71828182845904523536028747135266249775724709369995…$ as its base.

It is too difficult to remember and not easy to write it everywhere. So, he represented this irrational number by a letter $e$ and it is universally accepted.

$e = 2.71828182845904523536028747135266249775724709369995…$

Just write the symbol $e$ everywhere instead of writing this long number. So, the symbol e is basically called as a constant but it was introduced by the John Neper. Therefore, the constant $e$ is usually called as Napier constant.

2

#### Micro

$0.000001$ is one of the most famous small decimals.

A Greek symbol micro $(\mu)$ was introduced to represent millionth.

$$\mu = 0.000001 = 10^{-6} = \frac{1}{1000000}$$

The symbol $\mu$ represents this unique quantity. So, it is an example to a constant.

3

#### Pi

The value of the ratio of circumference to diameter of a circle is $3.1415926535897932384626433832795…$

It is an irrational number and constant even though the diameter of the circle is changed. A Greek symbol pi $(\pi)$ is used to denote this quantity.

$\pi = 3.1415926535897932384626433832795…$

The symbol $\pi$ is called as constant.

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