English UsageGrammar guide
If vs. Whether
“If” and “whether” overlap in many indirect yes-no questions, but they are not fully interchangeable. “Whether” is used in structures such as “whether to …” and “whether … or not,” while “if” also introduces ordinary conditional clauses.
Both can introduce many indirect yes/no questions, but “whether” is required in some structures, including before a to-infinitive; “if” also has the separate job of introducing conditions.
Key details
If Roleif also introduces conditional clauses
Shared Roleboth can introduce many indirect yes-no questions
Whether Only Patternswhether is used before a to-infinitive and in formal alternative structures such as whether or not
Further guidance
Indirect Question Boundary
In many indirect yes-no questions, both if and whether are possible.
Structure Boundary
Use whether, not if, before a to-infinitive; whether also handles explicit alternatives cleanly.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Whether — English Grammar Today (opens in a new tab)Cambridge Dictionary · Whether in indirect questions, alternatives, before infinitives and in whether-or-not structures