Grammar and mechanics · hard · v4.6.1

GRM-01

Use the serial comma (Oxford comma) in lists of three or more items.

Pass example

You can send emails, build landing pages, and manage contacts.

Fail example

You can send emails, build landing pages and manage contacts.

Relevant content types

Example pairs

Concrete before/after pairs observed in public style guides, each with inline attribution. See /sources for the full source list and licensing.

  • wayfinding · ui_labelall-rights-reserved

    Not this. Your's

    But this. Yours

    Primer: the canonical contraction confusion. Catching it keeps the tool credible. — GitHub Primer · Grammar

  • compliance_disclosure · long_form_copyCC0-1.0

    Not this. If a applicant meet the criteria...

    But this. If an applicant meets the criteria...

    USWDS: grammar errors in federal copy erode trust. Subject-verb agreement + a/an distinction. — USWDS · Plain language — Grammar

Sources

Style guides that shaped this standard. Each is listed on /sources with its license and opt-out path.

  • Mailchimp
  • GitHub Primer
  • USWDS
  • Microsoft Writing Style Guide

Version history

  1. v4.6.1 · 2026-04-23

    Per-standard version tracking introduced. Every standard starts at the library version current at introduction; bump per-standard when the rule text, examples, or content_type_notes change.

Related standards

Other standards in the Grammar and mechanics category.

  • GRM-02 — Spell out abbreviations and acronyms on first use in body copy and help content. Use the short form for subsequent mentions. Universally understood abbreviations (FAQ, URL, ZIP, LLC, IRS) and regulated accessibility terms (TTY) do not require expansion in any context. Internal or organization-specific abbreviations should always be expanded on a public-facing page. If the surrounding copy acknowledges the reader may not know a term, expand it.
  • GRM-03 — Use exclamation points sparingly. Never use more than one at a time, and never in error messages or alerts.
  • GRM-04 — Don't use ampersands in body copy unless they are part of a brand name. Ampersands are acceptable in headings, navigation labels, footer links, and other space-constrained UI elements where '&' is a conventional shorthand.
  • GRM-05 — Use numerals for numbers in body copy. Spell out a number only when it begins a sentence.
  • GRM-06 — Hyphenate number-unit compound modifiers before nouns. The unit takes singular form when hyphenated.

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