# Symbol of Natural numbers

I have been commonly using $$\mathbb {N}$$ and $$\mathbb {Z}^{+}$$ to denote natural numbers. Recently I have come across on some questions the symbol $$\mathbb {I}$$. I have checked various websites and have not found anything to do with the I symbol. Is it a proper symbol? I will be glad to know. Probably, it is used elsewhere in the world and I am unaware.

Note by Joel Tan
3 years, 1 month ago

MarkdownAppears as
*italics* or _italics_ italics
**bold** or __bold__ bold
- bulleted- list
• bulleted
• list
1. numbered2. list
1. numbered
2. list
Note: you must add a full line of space before and after lists for them to show up correctly
paragraph 1paragraph 2

paragraph 1

paragraph 2

[example link](https://brilliant.org)example link
> This is a quote
This is a quote
    # I indented these lines
# 4 spaces, and now they show
# up as a code block.

print "hello world"
# I indented these lines
# 4 spaces, and now they show
# up as a code block.

print "hello world"
MathAppears as
Remember to wrap math in $$...$$ or $...$ to ensure proper formatting.
2 \times 3 $$2 \times 3$$
2^{34} $$2^{34}$$
a_{i-1} $$a_{i-1}$$
\frac{2}{3} $$\frac{2}{3}$$
\sqrt{2} $$\sqrt{2}$$
\sum_{i=1}^3 $$\sum_{i=1}^3$$
\sin \theta $$\sin \theta$$
\boxed{123} $$\boxed{123}$$

Sort by:

$$\mathbb{I}$$ is used in India along with $$mathbb{N}$$ and $$\mathbb{Z}^{+}$$ to represent Natural numbers .

But as far as official use is considered , $$mathbb{N}$$ would be my choice .

- 3 years, 1 month ago

- 3 years, 1 month ago

I've not see $$\mathbb{I}$$ for ideals. They are often just $$I$$ or $$J$$.

Staff - 3 years, 1 month ago

Oh yeah, it does look different, I thought it was the normal capital I.

- 3 years, 1 month ago

Nope, not as far as I know. I try to refrain from using $$\mathbb{N}$$ unless it looks super ugly otherwise, to avoid any confusion. I take $$\mathbb{N} = \mathbb{Z}^{+} \cup \lbrace 0 \rbrace$$ as per the Peano axioms.

- 3 years, 1 month ago

The formal definition of natural numbers exclude 0.

- 3 years, 1 month ago