On another stackexchange site, I used the following phrasing:

I want to do X. It seems I can only do so when Y.

Someone edited the second sentence:

It seems that I can only do so when Y.

This made me realise that the edited form is perhaps more common -- but is my original phrasing grammatically incorrect? What role does "that" play in the second variation?


One use of the word that is as a complementizer, a part of speech that is a type of subordinating conjunction in traditional grammars. Complementizers introduce complement clauses, which are sentential clauses that may or may not stand alone and are the argument of the main verb:

  • I believe that she is a good person.
  • It seems that he can perform miracles.

In other words, the clause she is a good person (which stands alone as a valid sentence), is the argument of the verb believe. The argument of this use of believe is a complement clause, and so may optionally be introduced by the complementizer that.

When that is used as a complementizer, it is optional. Omitting or including the that complementizer is a stylistic decision. Here is a good article that can help elucidate the factors that go into the decision (also available as a podcast at the same link).

| improve this answer | |
  • 2
    Yes. A That-Complement is one of the four types of English Complement Clauses. The that is required only when the clause begins the sentence, where it's needed to mark a detour to a subordinate clause for the parser. That he was late is unfortunate vs *He was late is unfortunate. – John Lawler May 16 '13 at 14:47

Not the answer you're looking for? Browse other questions tagged or ask your own question.