Hook above

The hook is usually written to the right of the circumflex in conventional Vietnamese orthography.

If Vietnamese characters are unavailable, it is often replaced by a question mark after the vowel (VIQR encoding).

The Southern "dipping" tone is similar to the questioning intonation in English.

The hook above can be used as a tone marker, but is not regarded as part of the alphabet.

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Alexandre de Rhodes 's Dictionarium Annamiticum Lusitanum et Latinum ( Vietnamese–Portuguese–Latin dictionary ) showing bí without its tittle and bỉ with both a hook and tittle.