Mathematical Bold Italic Capital O 𝑶

Visual Description: The character is a bold, rounded O with a distinct italic slant. It has thick strokes and a smooth inner space that conveys weight and motion. In many fonts it appears slightly tilted, hinting at dynamism. It reads as a mathematical symbol rather than ordinary text.

Meaning & Usage: It marks a variable or a defined symbol in formulas. It can stand for an input, an index, or a function name in equations. In documentation, bold italic signals emphasis and distinction. In many calculators and software, it labels operations or comparisons for quick reference.

Historical Background: Such bold italic capitals come from a line of mathematical alphanumeric symbols used to separate variables from normal text. Designers aimed for legibility across screens and print. The goal was consistent rendering and clear differentiation in dense formulas, without tying the symbol to a fixed real world meaning.

Practical Use: Use it in formulas to name a function or input, or to mark a special case in an algorithm. In quick UI controls, bold italic O can be selected to switch modes or to compare values. In calculators, it helps users identify labeled fields, steps, or results & comparisons.

See our category page for related symbols.

Look‑alikes: O (U+4F).

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