Spanish uses only the acute accent, over any vowel: . This accent is used to mark the tonic (stressed) syllable, though it may also be used occasionally to distinguish homophones such as "si" ('if') and "sí" ('yes'). The only other diacritics used are the tilde on the letter , which is considered a separate letter from , and the diaeresis used in the sequences and —as in "bilingüe" ('bilingual')—to indicate that the is pronounced, , rather than having the usual silent role that it plays in unmarked and .