Doubt that / Doubt if / Doubt whether

To doubt is to be skeptical concerning something. We can use a clause after doubt.

Clauses after the verb doubt can be introduced by whether, if or that.

• I doubt that anyone can be clairvoyant.
• I doubt whether anyone can be clairvoyant.
• I doubt if anyone can be clairvoyant.
• I doubt that she will come this evening.
• I doubt whether she will come this evening.
• I doubt if she will come this evening.
• I doubt that he will repay the money.
• I doubt whether he will repay the money.
• I doubt if he will repay the money.

The conjunction can be dropped in an informal style.

• I doubt we will have enough money to buy a car. (= I doubt that we will have enough…)

After negative forms of doubt, we use ‘that’. ‘Whether’ and ‘if’ are not possible in this case.

• I don’t doubt that she will come.