What 𝕟 means
It is lowercase n in a mathematical double-struck style. In a formula, that style marks a separate symbol; the surrounding definitions tell you what the letter stands for.
Mathematicians also call this style blackboard bold. It lets a formula distinguish this n from other symbols; the formula supplies its particular role.
Why were the strokes doubled?
The doubled strokes made mathematical notation stand out without bold chalk. On a blackboard, writers retraced selected strokes; a typewriter could create a similar mark by striking a key twice.
The style moved from handwritten mathematics into print. Unicode encodes the full alphabet so mathematical distinctions can be preserved in plain text.
Plain n already had mathematical uses: in Giuseppe Peano's 1895 notation, n meant integers and N meant positive integers. That older use of plain letters does not define this double-struck form.
This belongs to mathematical or technical notation; its extra strokes carry a meaningful style distinction there.
Don't read it as ℕ: the familiar natural-number sign is uppercase.
Part of the collection
Don't confuse it with
3
Related characters
1
Questions people ask
2Why does 𝕟 become n?
It can: Unicode NFKC and NFKD compatibility normalization map 𝕟 to plain n, removing the style distinction. NFC leaves it unchanged.
Why can 𝕟 look different in another font?
It varies: mathematical fonts draw the double-struck alphabet differently, and Unicode does not prescribe one exact outline. The same encoded letter can have a simpler or more serifed look.
More like this
11
How to type or find 𝕟
- Also called
- blackboard bold n · double-struck n
- Search it as
- mathbb n · mathbb lowercase · unicode n
- Shows up in
- Anything that takes text · its shape is whatever your font draws
𝕟\1D55F\mathbb{n} only with a math font that supplies lowercase blackboard bold; the usual AMS font has capitals only.U+1D55F and commit it.Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.