Why isn't there a "Medium Small Black Circle" in Unicode

Question

I know this is maybe off-topic on SO, but I don't know where else to ask. The Unicode blocks Miscellaneous Symbols and Miscellanous Symbols and Arrows contain these characters:

• HEAVY LARGE CIRCLE (U+2B55) ⭕ (before emojis it used to look like ◯)
• BLACK LARGE CIRCLE (U+2B24) ⬤
• MEDIUM WHITE CIRCLE (U+26AA) ⚪
• MEDIUM BLACK CIRCLE (U+26AB) ⚫
• WHITE CIRCLE (U+25CB) ○
• BLACK CIRCLE (U+25CF) ●
• MEDIUM SMALL WHITE CIRCLE (U+26AC) ⚬

But there is no MEDIUM SMALL BLACK CIRCLE. Why is that? Is there an alternative for this symbol? (Ie. the same size as its white counterpart?)

Answer 1

According to the annotations in the chart for the Geometric Shapes Extended block, the set of differently sized black circles is ordered as follows:

1. U+22C5 DOT OPERATOR (⋅)
2. U+2219 BULLET OPERATOR (∙)
3. U+1F784 BLACK SLIGHTLY SMALL CIRCLE (🞄)
4. U+2022 BULLET (•)
5. U+2981 Z NOTATION SPOT (⦁)
6. U+26AB MEDIUM BLACK CIRCLE (⚫︎)
7. U+25CF BLACK CIRCLE (●)
8. U+2B24 BLACK LARGE CIRCLE (⬤)

⋅∙🞄•⦁⚫︎●⬤

Therefore, DOT OPERATOR serves as tiny black circle, BULLET OPERATOR serves as very small black circle, BULLET serves as small black circle, and Z NOTATION SPOT serves as medium small black circle.

These unifications with existing characters were implemented to cut down on the number of new additions needed when Wingdings/Webdings were incorporated into the standard.

Answer 2

Is there an alternative for this symbol?

Try • ∙ ⦁ 🞄

Why is that?

In the past, Unicode just collected existing character repertoires. If the originating did not have a medium small black circle, then for round-trip reasons Unicode would not have one, either.

You can get a definitive answer on the appropriate mailing list.