The Editor's Manual
Free learning resource on English grammar, punctuation, usage, and style.
Both “who” and “that” can refer to people. “Who” is preferred in formal usage.
Use commas to integrate closely related information into the flow of the sentence. Use parentheses to set off supplementary information or an afterthought from surrounding text. Use dashes to be emphatic or dramatic and make additional information or an aside stand out.
Use square brackets within parentheses to show brackets within brackets. In British style, round brackets are used within round brackets. Avoid using nested parentheses in U.S. writing.
Use “sic” to indicate a grammatical or spelling mistake in the original text of a quote. “Sic” is generally italicized in formal texts. Also enclose “sic” in brackets in formal writing.
Brackets enclose editorial comments and corrections, and any text added to a quote by someone other than the original writer. “Sic” in brackets indicates an exact reproduction. Brackets also set off parenthetical material that appears in text already within parentheses.
Use parentheses (or round brackets) to set off supplementary information from surrounding text. Such information should not be essential to the grammar of the sentence. Periods go within parentheses if they belong to the parenthetical matter but outside otherwise.
Both a colon and an em dash introduce new information that explains or builds upon something that precedes it. The colon is quieter; the dash is more emphatic and dramatic.
Avoid starting a sentence with an abbreviation in formal and academic writing. Use the full form instead, or rephrase. Acronyms, however, are acceptable in this position.
The first time you use an abbreviation in a text, write its full form and enclose the abbreviation in parentheses. If you believe readers will be more familiar with the abbreviated term, enclose the full form in parentheses instead.
An abbreviation is the shortened form of a term. It usually comprises the first letters of the words of a phrase or is the contracted form of a word.