Who vs. That vs. Which
Rule 1Who refers to people. That and which refer to groups or things.
Examples:
- Anya is the one who rescued the bird.
- Lokua is on the team that won first place.
- She belongs to an organization that specializes in saving endangered species.
Rule 2
That introduces essential clauses while which introduces nonessential clauses.
Examples:
- I do not trust products that claim "all natural ingredients" because this phrase can mean almost anything.
- We would not know which products were being discussed without the that clause.
- The product claiming "all natural ingredients," which appeared in the Sunday newspaper, is on sale.
- The product is already identified. Therefore, which begins a nonessential clause.
NOTE: Essential clauses do not have commas surrounding them while nonessential clauses are surrounded by commas.
Rule 3
If this, that, these, or those has already introduced an essential clause, you may use which to introduce the next clause, whether it is essential or nonessential.
Examples:
- That is a decision which you must live with for the rest of your life.
- Those ideas, which we've discussed thoroughly enough, do not need to be addressed again.
NOTE: Often, you can streamline your sentence by leaving out which.
Example:
- That is a decision which you must live with for the rest of your life.
Better:
- That is a decision you must live with for the rest of your life.