additional letters, beyond those of english braille, are for ł, for ' (glottal stop and ejective consonants), the french vowels with grave accents for the navajo vowels with acute accents (high tone), and for ogonek on the following vowel (nasal vowels, e.g. for ą, for ą́). is only used for the digit 6, as the letter 'f' does not exist in the navajo alphabet.