We've just launched our new Sales Writing Course!
Learn more


Business Grammar: That or Which?

One of the trickier grammar rules is the difference between the words that and which. Both serve a similar purpose of clarifying information in a sentence, but the meaning of the sentence can change depending on which word you use. 

There is an easy rule to remember:

  • That” introduces essential information in a “restrictive clause.”
  • Which” introduces extra information in a “nonrestrictive clause.”

“That” Example:

  • “Business writing expertise is the skill that is most valued.” The clause “that is most valued” is essential to the meaning of the sentence, so the correct word is “that.” You cannot remove the “that” clause without changing the meaning of the sentence.
  • A comma is never needed with that in a restrictive clause.

“Which” Example:

  • “We should all pay attention to David’s new product idea, which is likely to triple sales next year.” The second clause provides extra information, and it is not essential to the first clause. Therefore, “which” is correct.
  • A comma is required with which in a non-restrictive clause.


  • That = no comma = following information is essential.
  • Which = comma needed = following information is not essential.
Mary Cullen

About the author

Mary Cullen

Mary founded Instructional Solutions in 1998, and is an internationally recognized business writing trainer and executive writing coach with two decades of experience helping thousands of individuals and businesses master the strategic skill of business writing. She excels at designing customized business writing training programs to maximize productivity, advance business objectives, and convey complex information. She holds a B.A. in English from the University of Rhode Island, an M.A. in English Literature from Boston College, and a C.A.G.S. in Composition and Rhetoric from the University of New Hampshire.

Read Mary Cullen's Full Bio

Want to beacome a professional in Business Writing?

Whatever you write, Instructional Solutions teaches a proven process to synthesize and communicate complex information. For teams and individuals.