The Editor's Manual
Free learning resource on English grammar, punctuation, usage, and style.
Various phrases can begin an email, depending on formality (dear So-and-So, hi, hello, good morning). Using an appropriate salutation can set the right tone for your correspondence.
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 “who” as a relative pronoun to link a description to the person it describes. “Who” is used not just for people but also animals with names. “Who” can replace “whom” in informal usage.
Don’t use a comma before “who” when it presents information necessary to meaning (a restrictive clause). Do use a comma when “who” introduces an optional description (a nonrestrictive clause).
Don’t use a comma with “that,” either as a relative pronoun or a conjunction. “Which” usually introduces an optional description, which you should enclose in commas. No commas are used if “which” introduces essential information.
Use “which” to introduce a description. As a relative pronoun, “which” connects a relative clause to the noun it describes. Differences exist between American and British usage.
Use “that” as a relative pronoun in restrictive or defining clauses, which present information essential to meaning. Don’t use a comma before “that.”
The serial comma is used before the conjunction (“and,” “or”) that marks the final item in a series. Using it is optional, but it can sometimes affect the meaning of a sentence.
A period indicates a longer pause than a comma or a semicolon. Use a period to end a sentence and to mark the end of a thought or fragment. Also use periods in abbreviations and to separate initials before a surname.
Use commas to make lists, set off phrases, separate clauses, and indicate that a detail is nonessential in a sentence.