Iteration Value x Sub k xₖ

Semantic identity and intent

Characters to distinguish

• O — Big O
• o — Little O

Use xₖ in the right format

Meaning and usage

Marks an iterated or optimal value in numerical analysis and optimization.

Define the iteration index or optimality convention before using the compact symbol in an algorithm.

Pronunciation: iteration value x sub k

Formula examples

How to type Iteration Value x Sub k

Windows

Use Character Map or enter U+0078 + U+2096 in a Unicode-aware application.

macOS

Open Character Viewer with Control–Command–Space and search by the symbol name.

Microsoft Word

In an equation, type x_k and press Space when Word supports the command.

iPhone and iPad

Copy and paste xₖ, or use a math/LaTeX app. The standard iOS keyboard may not expose every mathematical symbol.

Android

Copy and paste xₖ, or use a math keyboard or LaTeX editor. Keyboard layouts vary by device and app.

Google Docs

For plain text, paste xₖ or use Insert → Special characters. For structured math, use the equation editor and verify x_k.

Excel

Paste xₖ into a cell or use Insert → Symbol when available. Ordinary cells preserve the character but do not interpret LaTeX commands.

Common mistakes

• Confirm the field-specific convention before using xₖ; Define the iteration index or optimality convention before using the compact symbol in an algorithm.
• For plain text, copy xₖ as U+0078 + U+2096; for structured equations, use x_k in math mode. A look-alike glyph or image can break search, accessibility, or parsing when the intended character is Iteration Value x Sub k.

When to use xₖ

• Use xₖ in plain text when a Unicode character is appropriate and the destination preserves U+0078 + U+2096.
• Use x_k in an equation editor when mathematical spacing or structure matters.
• Define the local meaning when Iteration Value x Sub k is used in numerical methods with a field-specific convention.

Look-alikes and related characters

• O — Big O
• o — Little O

Font and compatibility notes

Font coverage varies; verify the code point and destination rendering before publication.

Review and source notes

Quality tier: catalog

Last reviewed: 2026-07-23

Review method: Catalog review of character identity and notation mappings.

Verified against: Unicode Standard, Unicode mathematical notation guidance, and established LaTeX/MathML syntax.

Reference sources

• The Unicode StandardUnicode Consortium — Character identity, encoding, names, and conformance.
• Unicode Character Code ChartsUnicode Consortium — Code points and official character charts.

Frequently asked questions