whether – si

(Pronounced see)

Note: Not to be confused with sí (yes). The words are differentiated by an accent on the i in 'yes' in written Spanish. In spoken Spanish, the context of the sentence will determine the meaning. 

To remember that whether is pronounced see (si) in Spanish, use the following mnemonic:

I don't know whether to go to the seaside (si) or the mountains in this hot weather.