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Syntax: Which/That

Which “which” vs. “that” rules make you wish that grammar evaporated? Do “which” hunts sometimes feel like witch hunts?

  •  Trick: Imagine the noun (clauses) as a pie. Is the writer talking about the whole pie (which) or just slices of that pie (that)?


  • Rule/Explanation: Think of a that clause as slicing a pie. You’re taking a broad category and limiting (or restricting) it to only some members of that category: “I need to finish the book that you recommended.” That, in other words, comes before ESSENTIAL information: Without knowing that the writer finished the book you recommended, the reader wouldn’t know which book the writer is talking about.
  • Commas: Should not be used with restrictive clauses.


  • Rule/Explanation: A which clause tells you more about the whole pie: “Last night, I finally finished the book, which I thought was provocative.” Which, then, comes before NONESSENTIAL or NONRESTRICTIVE information: information that’s nice, but not necessary, for the reader to know.
  • Commas: Should be used with nonrestrictive clauses.

Example—Changed Meaning by Using Which vs. That:

  • Title of FTC Article on Noncompete Clauses: “Clauses, Which Hurt Workers”: The FTC is signaling that the entire noncompete-clause pie tastes bad.
  • Hypothetical Title of FTC Article on Noncompete Clauses: “Clauses That Hurt Workers”: The FTC would have conveyed that it wanted to slice the noncompete pie into pieces, keeping the good noncompete slices and throwing out the bad ones that hurt workers and harm competition.
General Rule: If the information adds to the whole pie, the phrase is nonrestrictive/nonessential and you need “which.” If the information limits the pie to only some of its slices, the phrase is restrictive/essential and you need “that.”

If you’d like additional examples and information, check out our cheat sheet here.