Reversed angle with underbar

A formula's notation supplies its role. ⦥ is a specialized mathematical sign; its shape alone does not name an operation. The MathML catalog associates it with the technical entity name range, but that label is not a reading rule for every formula.

Read the definitions around the formula. If the glyph is sent alone, it tells you only that the sender supplied a specialized mathematical sign, not which role to assign.

How was ⦥ used in mathematical publishing?

It appears in catalogs for mathematical typesetting. The ISO AMS collection is a catalog of named mathematical signs. MathML, a markup format for mathematical expressions, provides an entity for ⦥; Unicode-math, a TeX package for Unicode math, provides a command. Those labels let software refer to the character without assembling its shape from unrelated pieces.

How can I type ⦥?

Use a Unicode editor or a math-markup command. LaTeX, a formula typesetting system, accepts \revangleubar with a Unicode-math setup; the command goes in your source, and the typesetter renders the character.

HTML or MathML tools can use the range entity or a Unicode character reference when their serializer supports it. A character map or Unicode insertion feature in your editor is another route.

If ⦥ appears as an empty box or fallback mark, the font or app may not support it. Use a font that includes the glyph or provide a web font with coverage.