Ordinal Numbers
The stable decision is recognizing an ordinal and then applying the required style. The suffix belongs to numeral ordinals, but whether to spell an ordinal out is a house-style choice rather than a universal English rule.
Ordinal numbers express order or position, such as “first,” “second,” or “21st.” How they are written depends on the governing style: word-versus-numeral thresholds, dates, centuries, publication editions, and accessibility conventions can differ.
Key details
Important caveats
Boundary
Do not treat one style manual’s threshold as universal; dates, centuries, names, editions, and technical contexts can use different conventions.
Further guidance
Decision Path
Use the governing style for word-versus-numeral treatment, then form numeral suffixes correctly when numerals are required.
Diagnostic
Ask whether the number expresses position in an ordered sequence rather than quantity.
Worked Example
“The 21st revision” is an ordinal because it identifies position in a sequence; “21 revisions” is cardinal because it gives a quantity.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Ordinal numbers (opens in a new tab)Australian Government Style Manual · Defines ordinal numbers as order/position terms and gives current spelling, numeral, suffix, date, accessibility and exception guidance.
- Quick guide: numbers (opens in a new tab)Australian Government Style Manual · Summarizes current general-content number conventions and explicitly distinguishes ordinal-number treatment from other number styles.