Infinity Symbol
The infinity symbol is a mathematical symbol that represents an infinitely large number.
The infinity symbol is written with the Lemniscate symbol:
∞
It represents an infinitely positive big number.
When we want to write an infinitely negative number we should write:
-∞
When we want to write an infinitely small number we should write:
1/∞
Is infinity a real number?
Infinity is not a number. It does not represent a specific number, but an infinitely large quantity.
Infinity rules & properties
| Name | Key type |
|---|---|
| Positive infinity | ∞ |
| Negative infinity | -∞ |
| Infinity difference | ∞ - ∞ is undefined |
| Zero product | 0 ⋅ ∞ is undefined |
| Infinity quotient | ∞ / ∞ is undefined |
| Real number sum | x + ∞ = ∞, for x∈ℝ |
| Positive number product | x ⋅ ∞ = ∞, for x>0 |
How to type infinity symbol on keyboard
| Platform | Key type | Description |
|---|---|---|
| PC windows | Alt+236 | Hold the ALT key and type 236 on the num-lock keypad. |
| Macintosh | Option+5 | Hold the Option key and press 5 |
| Microsoft word | Insert > Symbol > ∞ | Menu selection: Insert > Symbol > ∞ |
| Alt+236 | Hold the ALT key and type 236 on the num-lock keypad. | |
| Microsoft excel | Insert > Symbol > ∞ | Menu selection: Insert > Symbol > ∞ |
| Alt+236 | Hold the ALT key and type 236 on the num-lock keypad. | |
| Web page | Ctrl+C, Ctrl+V | Copy ∞ from here and paste it in your web page. |
| Ctrl+C, Ctrl+V | Copy ∞ from here and paste it in your Facebook page. | |
| HTML | ∞ or ∞ | |
| ASCII code | 236 | |
| Unicode | U+221E | |
| LaTeX | \infty | |
| MATLAB | \infty | Example: title('Graph to \infty') |
Infinity in set theory
Aleph-null (
) is the infinite number of elements (cardinality) of the natural numbers set (
).
Aleph-one (
) is the infinite number of elements (cardinality) of the countable ordinal numbers set (ω1).