No. Abbreviation and Punctuation
“No.” is a conventional abbreviation for “number” in Chicago-style contexts. The guide keeps it distinct from the number sign and from shortened forms such as num. or n., which may carry other meanings.
When you need a conventional abbreviation for “number,” Chicago recommends “no.”; capitalization then follows its position and use, as in “No. 45.”
Key details
Important caveats
Style Boundary
The number sign (#) and other shortened forms have additional meanings; use them only when the relevant style or context calls for them.
Further guidance
Capitalization
Capitalize it as “No.” when normal sentence/title context requires an initial capital, as in labels such as “No. 45.”
Practical Application
Use the conventional “No.” form for “number” when that is what your style requires, and capitalize it according to position/use. Keep it distinct from the number sign (#) and from unrelated abbreviations.
Preferred Form
Chicago recommends “no.” in most contexts where the word “number” needs to be abbreviated.
Reader Check
Are you abbreviating the word “number,” and does the governing style specifically call for “No.”?
Worked Example
Write “No. 45” when following the reviewed abbreviation style. Do not substitute “#45” merely because both can identify a numbered item; the symbols have different style conventions.
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.
- Chicago Q&A — abbreviating number (opens in a new tab)The Chicago Manual of Style / University of Chicago Press · Chicago recommends no. as the common abbreviation for number in most relevant contexts