The diphthongs are as follows:
ai hai (winter) aisle
ei séí (sand) weigh
oi 'ayóí (very) Joey
The diphthongs oi (as in Joey) will frequently be heard as ui (as in
dewy) in certain sections of the reservation. However, since the related
word ayóó is always of one value, this spelling has been standardized.
In a similar way, the diphthongs ei and ai are not universally
distinguished. For example, the word for sand, séí will be pronounced
sáí by some Navahos.