What 𝐊 means
Bold K marks a math variable; the formula defines its role. Boldface can identify a vector (a quantity with components), a matrix (a rectangular grid of numbers), or another object, depending on the author’s convention. The letter K itself does not name a particular thing.
Unicode gives this bold math K its own character so plain-text formulas can preserve the style distinction. It is meant for mathematical and technical notation; ordinary prose can use a normal K with bold formatting.
How did bold type become a math distinction?
Mathematicians used letter styles to separate quantities. In 1881, mathematician J. Willard Gibbs used Greek letters for vectors and Latin letters for scalars (single-number quantities). By 1901, his student Edwin Wilson used bold and plain versions of a letter to distinguish a vector from its magnitude, or size. In 1921, Hermann Weyl used bold letters for vectors and plain letters with a small index below for their components.
These are examples from a changing convention. The bold K in a modern formula has whatever role that text defines.
Part of the collection
Don't confuse it with
1
Questions people ask
2Why does 𝐊 turn into plain K?
NFKC (Unicode’s compatibility-normalization form) can do that: it maps 𝐊 to plain K, removing the style distinction. NFC leaves it unchanged.
Why does 𝐊 look different in another font?
The font draws the glyph; Unicode defines the character and its math style, not one exact outline. Two fonts can therefore make 𝐊 look different while representing the same character.
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How to type or find 𝐊
- Search it as
- bold k · math bold k · unicode bold k · bold letter k · fancy k
- Shows up in
- Anything that takes text · its shape is whatever your font draws
𝐊\1D40ACodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.