Mathematical Double-Struck Small D 𝕕

Visual Description: A small letter d rendered in a double-struck style appears with extra lines and a thick stroke. It looks like a regular d but with stylized weight. The shape is used for emphasis in math fonts. In design, it signals a typographic variant. It also serves as a visual cue in slides and notes.

Meaning & Usage: This symbol is mainly a typographic variant rather than a distinct quantity. In math notation, double-struck letters often designate special sets or operators. A double-struck d may be used to distinguish a differential symbol or a variable in a specific text. Some designers discuss its readability and contrast.

Historical Background: The double-struck style emerged in early printing and was carried into digital typesetting with Unicode. It appears in the Mathematical Alphanumeric Symbols block. The goal is to provide a formal look for objects in formulas. This approach is common in textbooks and math software. Users may encounter it when fonts or keyboards include mathematical alphabets.

Practical Use: In formulas, you insert it with a math editor or a keyboard shortcut that switches to a double-struck font. On calculators and apps with symbol palettes, you can pick this style for emphasis. It signals a special role, useful for comparisons or to mark a chosen set. It's mainly cosmetic in function, but it helps organize ideas.

See our category page for related symbols.

Look‑alikes: d (U+64).

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