Aunque ambas palabras significan lo mismo, el condicional si, hay unas pequeñas diferencias que hace que dependiendo del momento puedas utilizar una u otra. Como siempre, vamos a ver cuáles son esas pequeñas diferencias:
Se puede usar if o whether para responder a preguntas cuya respuesta es si-no y preguntas indirectas con “or”. Aunque en este caso if es más común que whether:
- Call the butchers around town and find out if any of them sell oxtail.
- I rang Jaime from the station and asked if I could drop in to see him before going back or if he’d meet me.
A menudo, se prefiere utilizar whether en contextos más formales:
- The teachers will be asked whether they would recommend the book to their classes.
O en reuniones (sobre todo relacionados con los negocios):
- Jamie read a letter that he’d written and the board discussed whether it should be mailed.
Se prefiere el uso de whether con “or” cuando hay más de una alternativa en una pregunta indirecta:
- After the election, we asked whether the parties should change their leaders, their policies, or both.
Se puede utilizar “or not” con if y whether para expresar alternativas. Con whether, se puede usar “or not” inmediatamente después de whether o al final de la frase. Con if podemos usar “or not” solamente al final de la frase.
- I called Beck to find out whether or not he really did go to Moscow.
- I called Beck to find out whether he really did go to Moscow or not.
- I called Beck to find out if he really did go to Moscow or not.
Se usa whether y no if delante de “to + infinitive”, a menudo cuando se refiere a planes o decisiones futuras.
- I was wondering whether to go for a walk.
- Some financial decisions, such as planning a pension, need to be taken as early as possible. Others, such as whether to move house, can probably only be made much later.
Se utiliza whether y no if después de preposiciones:
- Later I argued with the doctor about whether I had hit my head, since I couldn’t remember feeling it.
- The police seemed mainly interested in whether there were any locks on the windows.
Se utiliza if o whether para introducir “clauses” después de verbos que indiquen duda.
- I don’t know if I can drive. My head really hurts.
- I didn’t prune the rose bush this year so I doubt if we’re going to have many flowers. (‘prune’ means cut back)
- We’ll have plenty of photographs to show you but I’m not sure whether we’ll be able to learn very much from them.
Fuente: Cambridge