Mathematical Italic Capital I 𝐼

Visual Description: The glyph is a tall, slender I with an italic tilt. It looks like a standard capital I, but slanted to indicate a variable. The stroke is clean and even, without heavy serifs in most math fonts. It blends with alphabetical symbols in formulas and on calculators' displays.

Meaning & Usage: This symbol represents a variable in math writing. It does not denote a fixed value. It can stand for a quantity that varies with context. In equations and inequalities, it pairs with numbers, vectors, or other variables, like A & B relations or I = f(x). In quick notes, it helps separate items in a list of symbols.

Historical Background: The idea of italic variable letters grew as math notation expanded in print. Mathematicians and printers created consistent shapes to distinguish variables from constants. The system evolved with type design and digital fonts, so you can find this letter in many math sets. It remains common in modern textbooks and software.

Practical Use: In formulas, this italic I stands for a variable or function. It helps show unknowns in algebra and identities in proofs. In calculators and math editors, you insert it with a symbol button or a quick toolbar. It supports operations and comparisons by clarifying which quantity is being referred to.

See our category page for related symbols.

Look‑alikes: l (U+6C).

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