A style guide is a set of rules and standards that tells you how to write, format, or present things in a consistent way. Think of it as an instruction manual for making sure everyone working on the same project follows the same patterns.

Newspapers use style guides to decide whether to write “10” or “ten,” whether to capitalize “president,” and how to format dates. This ensures that every article in the paper looks and reads like it belongs there. Schools often have style guides for research papers that tell you how to cite sources, whether to use footnotes, and how to format your bibliography. Companies create style guides for their websites so every page uses the same fonts, colors, and tone of voice.

Style guides aren't about right or wrong in an absolute sense. The Associated Press style guide makes different choices than the Chicago Manual of Style, and both are correct within their own systems. What matters is consistency: following the same rules throughout a single piece of writing or across an organization.

When you follow a style guide, your work looks more professional and polished. Your readers don't get distracted by inconsistencies like seeing “okay,” “OK,” and “o.k.” all in the same essay. The guide makes thousands of small decisions for you so you can focus on the content rather than agonizing over formatting details.