A who/which clause is an adjectival clause found in the middle of a sentence. The entire w/w clause acts like an adjective, which modifies a noun or pronoun. A w/w clause should come immediately after the noun or pronoun it modifies. The w/w clause is set off with commas.
Recall that any clause is a group of related words that has a subject and a verb. In a w/w clause, the subject of that clause is either ‘who” or “which”. Use “who” when referencing a person or a animal that is personified; use “which” to reference everything else.
Examples:
* Jeremy, who is wearing a red shirt, usually wears blue or grey.
“Who is wearing a red shirt” is the w/w clause. Note that it comes immediately after the noun it modifies, “Jeremy”.
* I visited the International Wolf Center, which is located in Ely, Minnesota.
“Which is located in Ely, Minnesota” is the w/w clause. It modifies International Wolf Center.
* I’ll share my cookies with you, who has no dessert in your lunchbox.
“Who has no dessert in your lunchbox” is the w/w clause. It modifies “you”.
Incorrect examples:
* Who is coming with us?
There is nothing in the sentence before the word “who” that can be modified.
* I don’t know which pair of shoes to wear.
In this example, “know” is a verb, so “which pair of shoes to wear” cannot be an adjectival clause and thus is not a w/w clause. Another clue that this is not a w/w clause is that you cannot put a comma between “know” and “which”.