Do you need a comma with Who? Sometimes yes, sometimes no, depending on what who is doing in the sentence. These three sample sentences demonstrate when to use commas, or not to use commas, with who.
- I am an editor, who is a person with the task of improving clarity in writing.
- I am an editor who loves commas.
- As an editor who loves commas, I put in all the required commas to reduce potential reader confusion.
Comma with WHO
Sentence 1, with a comma before who, has one message: I am an editor. And what is an editor? Editor is defined as a person with the task of improving clarity in writing. In this sentence, the clause beginning with who provides descriptive information about editors.
As a non-restrictive clause, this expression doesn’t tell which editor is being described, i.e., it doesn’t restrict the reader’s attention from a group of things to a single thing. Rather, it is providing a definition.
The comma here follows Zen Comma rule U: Use commas to separate non-restrictive clauses beginning with who.
No comma with WHO
You don’t need a comma with who if the word is starting a “restrictive clause.” A restrictive clause helps to indicate one thing from among similar things, i.e., which thing you are writing about.
Sentence 2, with no comma before who, describes a group of people called editors. Which one am I? How am I different from other editors? What type of editor am I? I am an editor who loves commas.
Who loves commas is required information to identify me from the rest of the editors. As a restrictive clause, who loves commas restricts the reader’s attention from all editors to one particular editor: me, in this case.
This is the same situation as in sentence 3. Again, who loves commas is required information to tell the reader which editor is being discussed.
With no commas before who, sentences 2 and 3 follow Zen Comma rule V: Don’t use commas to separate restrictive clauses beginning with who.
Need help with commas? Get Zen Comma, an instructive reference guide on the 17 major uses and misuses of commas, available in PDF and Kindle formats. Read more about Zen Comma.