Mathematical Double-Struck Capital J 𝕁

Visual Description: The character is a tall J with double strokes. The two lines run parallel from top to bottom. It has rounded terminals and a bold, blocky look. The double lines create a chalkboard bold effect. The glyph stands out against ordinary letters. It reads as a formal math symbol.

Meaning & Usage: In math notation, this style marks special objects or operators. A double-stroke J can denote a named object or a function in a symbol list. It signals distinction beyond ordinary variables. Readers expect a formal, utility driven meaning and a clear context in formulas.

Historical Background: The double-stroke look grew from chalkboard signs used in classrooms. Typographers later adopted the style for print to preserve visibility on dense math pages. It became part of a broader family of distinct, bold letters that denote important mathematical objects. The idea spread through textbooks and font collections.

Practical Use: In formulas, the symbol may denote a special object or operator in an equation. In calculators and math apps, it can appear as an icon or button for a unique function or a specific set. Quick UI controls can switch notation, compare results, or highlight key steps with a bold marker. This helps clarity.

See our category page for related symbols.

Look‑alikes: J (U+4A).

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