The Question That Never Goes Away

Few grammar questions generate as much quiet confusion as the choice between "who" and "that" in relative clauses. Should you write "the person who called" or "the person that called"? Is one wrong? Are both fine? The answer is more straightforward than most style debates suggest, but it comes with a useful nuance.

The Core Rule

Use who (or whom) when referring to people. Use that when referring to things, animals, or groups treated as entities rather than individuals.

  • "The developer who wrote the original code has left the company."
  • "The bug that crashed the server has been patched."

This rule covers the vast majority of cases. If the antecedent, the noun being described, is a human being, reach for "who." If it is an object, concept, or non-human entity, use "that."

Why "That" for People Is Not Technically Wrong

Here is the nuance: using "that" to refer to people is not a grammatical error. It has a long history in English. Shakespeare used it. The King James Bible uses it. Merriam-Webster's usage guide notes that "that" referring to persons is "standard." So "the person that called" is not incorrect.

However, modern style guides, including the Chicago Manual of Style, the AP Stylebook, and most editorial standards, prefer "who" for people. The reason is not grammar but clarity and courtesy. "Who" signals that you are talking about a person, and readers process it faster. "The employee who reported the issue" reads more naturally than "the employee that reported the issue."

When "That" Is the Better Choice for People

There is one context where "that" works better even with human antecedents: when you are referring to a type or category of person rather than a specific individual.

  • "She is the kind of leader that inspires loyalty." (Here "that" feels natural because the focus is on the type.)
  • "Anyone that disagrees should speak up." (Acceptable because "anyone" is indefinite.)

These uses are defensible, but if you prefer consistency, substituting "who" in these sentences also works perfectly.

The Practical Takeaway

Default to "who" for people and "that" for everything else. You will be correct by every major style guide, your writing will be clearer, and you will never need to second-guess the choice. Save your mental energy for harder decisions.