Lojban vowels also occur in pairs, where each vowel sound is in a separate syllable. These two vowel sounds are connected (and separated) by an apostrophe. Lojban vowel pairs should be pronounced continuously with the [h] sound between (and not by a glottal stop or pause, which would split the two vowels into separate words).
All vowel combinations are permitted in two-syllable pairs with the apostrophe separating them; this includes those which constitute diphthongs when the apostrophe is not included.
The Lojban vowel pairs are:
a'a a'e a'i a'o a'u a'y
e'a e'e e'i e'o e'u e'y
i'a i'e i'i i'o i'u i'y
o'a o'e o'i o'o o'u o'y
u'a u'e u'i u'o u'u u'y
y'a y'e y'i y'o y'u y'y
Vowel pairs involving “y” appear only in Lojbanized names. They could appear in cmavo (structure words), but only “.y'y.” is so used — it is the Lojban name of the apostrophe letter (see Chapter 17).
When more than two vowels occur together in Lojban, the normal pronunciation pairs vowels from the left into syllables, as in the Lojbanized name:
5.1) meiin.
mei,in.
Example 5.1 contains the diphthong “ei” followed by the vowel “i”. In order to indicate a different grouping, the comma must always be used, leading to:
5.2) me,iin.which contains the vowel “e” followed by the diphthong “ii”. In rough English representation, Example 5.1 is “May Een”, whereas Example 5.2 is “Meh Yeen”.