Your word processor assumes that a word space marks a safe place to flow text onto a new line or page. A nonbreaking space is the same width as a word space, but it prevents the text from flowing to a new line or page. It’s like invisible glue between the words on either side.
|Mac OS Word
|control + shift + space bar
|option + space bar
|control + space bar
Put a nonbreaking space before any numeric or alphabetic reference to prevent awkward breaks. Recall this example from paragraph and section marks:
1782, offer a full refund to buyers. But ¶
49 of the contract offers another option.
§ 1782, offer a full refund to buyers. But
¶ 49 of the contract offers another option.
In the top example, normal word spaces come after the § and ¶ symbols, and the numeric references incorrectly appear on the next line.
In the bottom example, nonbreaking spaces come after the § and ¶ symbols. This time, the symbols and the numeric references stay together.
Use nonbreaking spaces after other reference marks
In citations, use your judgment. In the citation