Mathematical Double-Struck Capital K 𝕂

Visual Description: The symbol appears as a bold, double-struck K. It shows two vertical strokes with extra lines that distinguish it from a normal letter. In standard math fonts, it resembles a blackboard bold letter used for special objects. It reads clearly in formulas, calculators, and display panels. This helps readers spot the symbol quickly in dense text.

Meaning & Usage: These letters signal special math objects. K is commonly used to denote a field or a distinguished set. In equations, K may stand for the object under study. In software, it helps distinguish the object from ordinary letters. In notation, it often marks a canonical choice.

Historical Background: The double-struck style grew from classroom practice of highlighting key objects on blackboards. Digital versions were added to Unicode and math fonts to preserve the look in print and on screen. The idea is to keep a clear, consistent cue across different tools and formats. Its presence signals formal treatment, not casual writing.

Practical Use: In math editors, you can enable a double-struck font to mark K and related symbols. In calculators and notebook apps, a quick UI control may switch notation for a problem. Use this style to compare objects, state formulas, or denote a field in proofs. Developers may provide presets for quick insertion.

See our category page for related symbols.

Look‑alikes: K (U+4B).

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