The Kharulian word for “vowel letter” is saghyázlara [saˈʝaz.ɫa.ra], literally “that is smooth”. The word is also used for “vowel sound”, but it only applies to vowel sounds that appear in the written form. For example, the word saghyázlara is spelled s-khy-a-s-l-r-a, so a Kharulian would consider it to only have two “vowels”.
Whether a vowel is written or not has to do with its morphological prominence. Some vowels are morphologically stable, appearing across all forms of a root; for example, saghyázlara is based on the verb root khyáral, and all forms of khyáral have the first a in them.
Other vowels are morphologically fickle, and pop in and out of existence depending on the affixes that have been attached; the second a in khyáral is an example, since it disappears in suffixed forms like sa-ghyázl-ara (the [z]/[r] alternation is a regular phonological rule that affects all underlying /s/). Kharulian
scholars don’t think of such fickle vowels as vowels; instead, they think of them as “spacers” that are only there to make the word pronounceable.