For example:
- 0041 LATIN CAPITAL LETTER A
- 1D400 MATHEMATICAL BOLD CAPITAL A
- 1D49C MATHEMATICAL SCRIPT CAPITAL A
- 1D4D0 MATHEMATICAL BOLD SCRIPT CAPITAL A.
I read that Unicode tries not to encode character presentations.
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1I am not exactly sure what your issue is, but if this is about encoding instead of design, this question is not well suited for this site. It may be suited for Super User, but I would guess that you already find answers here or here.– Wrzlprmft ♦Commented Sep 30, 2021 at 14:30
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1I suppose it could be a design question if it can be interpreted as "Why do I need to use a Cyrillic А when a Latin A will do just as well?" but that turns the question on its head (as I've tried to demonstrate in my answer).– Andrew LeachCommented Sep 30, 2021 at 16:20
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@Wrzlprmft I don't ask how to find a code point in Unicode. I'm asking why Unicode designers included these code points, what was their rationale. I found one relevant sentence in your links, “Those characters are not intended for regular Latin-alphabet text but for phonetics, Cyrillic-alphabet text, for use as mathematical symbols (representing variables), or similar”. Mathematical formulas seem like a valid reason; I'll address it in the answer. My native language is written in Cyrillic, and I don't know what they are talking about.– beroalCommented Oct 1, 2021 at 15:35
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2 Answers
I believe the question is asking why A, 𝐀, 𝒜 and 𝓐 have different code points when they are the same character in different fonts.
The answer is that they are not the letter A in different fonts. They are different characters in a single font (assuming the font includes them and they can be displayed: if not, then a substitution might occur).
It is a more extreme example of the phenomenon demonstrated by Latin A at 0041 and Cyrillic А at 0410.
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1Because they have different purposes. You can't write A where you should write 𝒜, just as you can't write D where you actually mean Δ, or ŵ instead of w, or even L instead of Ł. Commented Oct 1, 2021 at 15:43
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These characters are needed for mathematical formulas to display the way mathematicians expect them to. The alphabets encoded at the other code points are only basic alphabets, and don't include for instance ÀÁÄÂÆÃÅĀ.
For this reason, you're advised it's bad practice for accessibility to use these letters on social media, Twitter or other platforms which don't have character formatting, as screen-readers used by blind people can't read them.
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2it's bad practice for accessibility to use these letters on social media … – except of course if you want to use them to represent mathematical symbols.– Wrzlprmft ♦Commented Oct 1, 2021 at 13:24
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So U+1D400 “MATHEMATICAL BOLD CAPITAL A” and others exist because mathematics is a script distinct from Latin, like Latin is distinct from Cyrillic. Then why is there no “MATHEMATICAL SMALL A”? Instead, mathematicians use U+0061 “LATIN SMALL LETTER A” as a variable name.– beroalCommented Oct 1, 2021 at 15:42
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1Hm. There actually is U+1D44E “MATHEMATICAL ITALIC SMALL A” ☺. There are “mathematical” Greek letters too.– beroalCommented Oct 1, 2021 at 16:05