Knowing whether to use “whether” or “if”

When introducing a clause indicating uncertainty after a verb, is it better to use “whether” or ‘if”? That’s a question the editors at Precision Science Editing are frequently asked. Although the two words are often used interchangeably in informal writing, as the American Heritage Guide to Contemporary Usage and Style points out, ”Whether has long been the preferred word in more formal contexts.” “Grammar Girl” Mignon Fogarty has the following guideline to offer: “Use ‘if’ when you have a conditional sentence and ‘whether’ when showing that two alternatives are possible.” Compare these two statements: The laboratory assistant didn’t know if the specimens would arrive on Friday or Saturday. (This statement implies the specimens may arrive on Friday, on Saturday, or not at all!) The laboratory assistant didn’t know whether the specimens would arrive on Friday or Saturday. (This statement implies there were only two possibilities: the specimens would arrive on Friday or they would arrive on Saturday.  The GMAT Tip of the Week, a weekly column that includes advice on taking the Graduate Management Admission Test, explains it this way: Use “if” in a conditional sentence to show that one thing will happen if something else happens. Use “whether” to show that two alternatives are possible. If it rains, they will collect stormwater samples. They will do their field sampling regardless of whether it rains. The word “whether” can be used: After a preposition: Have you settled the question of whether there is a direct causative relation between Chlamydia trachomatis and PID? …

Rick of the Precision Science Editing blog teamKnowing whether to use “whether” or “if”