Math Font, Unicode, Gothic Letters, Double Struck, 𝔄 𝔅 ℭ

Math Letters in Unicode Basic Multilingual Plane

In math, there's these special styled letters:

Double Struck (aka Blackboard bold): ℂ ⅅ ℍ ℕ ℙ ℚ ℝ ℤ ⅆ ⅇ ⅈ ⅉ

Gothic (aka Blackletter, Fraktur): ℭ ℑ ℌ ℜ ℨ

Scripted: ℬ ℰ ℱ ℋ ℐ ℒ ℳ ℘ ℛ ℯ ℓ ℊ ℴ

Note that the above does not contain the full alphabets A to z. The above characters are in Unicode's “Basic Multilingual Plane”. (BMP. Their Unicode number can be expressed by 4 digits of hexadecimal. (See also: UNICODE Basics: What's Character Encoding, UTF-8, and All That?))

Complete Gothic Style Alphabet

The full set of letters from A to z of these styles is also in Unicode, but is outside of BMP, thus are currently not widely supported.

Here's the complete set of Gothic styled alphabet. (those in parenthesis are in BMP)

Uppercase: 𝔄 𝔅 ℭ 𝔇 𝔈 𝔉 𝔊 ℌ ℑ 𝔍 𝔎 𝔏 𝔐 𝔑 𝔒 𝔓 𝔔 ℜ 𝔖 𝔗 𝔘 𝔙 𝔚 𝔛 𝔜 ℨ

Lowercase: 𝔞 𝔟 𝔠 𝔡 𝔢 𝔣 𝔤 𝔥 𝔦 𝔧 𝔨 𝔩 𝔪 𝔫 𝔬 𝔭 𝔮 𝔯 𝔰 𝔱 𝔲 𝔳 𝔴 𝔵 𝔶 𝔷

these are in BMP: ℭ ℌ ℑ ℜ ℨ

If your browser does not display them, then you may need to need to install the STIX Fonts. It's a font set specially designed for math. Home page is at www.stixfonts.org. After you install the font, you can choose “StixGeneral”. (be sure to follow the instruction on Windows. You can't just drop the font in the font folder)

• The Gothic styled letters is also known as “Blackletter”. But Gothic-style is a more intuitive name.
• The Double Struck (ℝ ℂ) is also known as “Blackboard bold”. Double Struck is a better name. But even better is “double stroke”.

Complete Double Struck Alphabet

𝔸 𝔹 ℂ 𝔻 𝔼 𝔽 𝔾 ℍ 𝕀 𝕁 𝕂 𝕃 𝕄 ℕ 𝕆 ℙ ℚ ℝ 𝕊 𝕋 𝕌 𝕍 𝕎 𝕏 𝕐 ℤ

𝕒 𝕓 𝕔 𝕕 𝕖 𝕗 𝕘 𝕙 𝕚 𝕛 𝕜 𝕝 𝕞 𝕟 𝕟 𝕠 𝕡 𝕢 𝕣 𝕤 𝕥 𝕦 𝕧 𝕨 𝕩 𝕪 𝕫

𝟘 𝟙 𝟚 𝟛 𝟜 𝟝 𝟞 𝟟 𝟠 𝟡

Slanted, Bold, Variants

In Unicode, besides the sets of {gothic, double struck, scripted} forms for the whole Latin alphabet, there's also slanted and bold and “slanted and bold” variants, as actual Unicode characters. They are all outside of BMP. You can see them at Mathematical Alphanumeric Symbols.

I would advise to not use these stylistic variants as much as possible. Using slanted letter for variables in math is not semantically meaningful, in works such as Calculational Proofs notation or computer proof and computer algebra languages. Slanted letters as variables contribute to the problem of traditional math notation. The essential reason it's bad is because in traditional math notation, or the use of slanted font for variable, it basically treats the notation as visual glyphs of ideas, not as a language with structure and grammar. 〔☛ The TeX Pestilence (the problems of TeX/LaTeX)〕