Mathematical Double-Struck Capital Y 𝕐

Visual Description: The symbol is a bold Y with a double stroke, like a blackboard bold letter. It has two parallel verticals linked by a diagonal arm, giving it a sturdy, almost architectural look. It stands out from ordinary letters in print and on screens, signaling a special object in math.

Meaning & Usage: In mathematics, this version marks a distinguished object, such as a chosen set or a special space. It is not a plain variable. Writers use it alongside other double struck letters to keep notation clear in proofs, equations, and diagrams. UI tools may insert it by a button.

Historical Background: The double struck look arose as writers sought to distinguish certain mathematical objects from ordinary text. Early typography emphasized strong, legible marks on blackboards and pages. Over time, publications adopted a consistent double stroke for standard sets and important symbols, creating a recognizable style for readers.

Practical Use: In teaching, calculators, and math editors, you will see quick UI controls for inserting this symbol or swapping it with other notation. Use it to name a special set, to compare objects, or to highlight a key concept in formulas and proofs. It helps readers focus on structure.

See our category page for related symbols.

Look‑alikes: Y (U+59).

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