Mathematical Double-Struck Small F 𝕗

Visual Description: The symbol is a small f drawn with double strokes, like a blackboard bold letter. It has extra vertical lines and a rounded loop, giving it a strong, solid look on math pages. On calculators or math editors, it reads as a familiar f but thicker and more formal.

Meaning & Usage: This symbol is a double-struck form of the letter f. In math, double-struck letters usually denote special objects. The small f can denote a particular function or a space of functions, depending on the author. Writers use it to distinguish a named object from ordinary variables in equations.

Historical Background: The double-struck style arises from print where lines surround letters to indicate special meaning. In modern math typesetting, fonts and alphabets reproduce the look. The idea is to mark objects as distinct from ordinary symbols. The form travels from print to screens and to everyday math tools.

Practical Use: In formulas, you may see this f as a special function or as a function space. Quick UI controls in calculators and software can toggle bold or double-stroke styles to compare objects. The symbol helps quick recognition in proofs, lists, and panels for operations like evaluation.

See our category page for related symbols.

Look‑alikes: f (U+66).

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