arsham wrote:The diphthongs ow and ei
ey/ei is not a diphthong. "ey" composes of phonemes "e" and "y". It is easy to prove it: if you replace "y" with another phoneme, you get a new word: mey -> mes, meh. Although it is my personal opinion but I have also seen such an opinion from well-versed people like Mr. Yadollâh e Samare in his book "Âvâshenâsi ye zabân e Fârsi".
If you want to consider "ey" as a diphthong, you must also do so for other "vowel+y" combinations: juy, xoy, jây.
I think you are taking "ei" from Spanish. Am I right?
Persian has only one diphthong, which is "ow" (I'll write it with ô in the following examples). However some say that "ow" is not actually a diphthong and it comprises of "o" and "v" (like Mr. Samare). Anyway, I personally think that it is a diphthong because it has a phonemic value: replace "ow" with another phoneme and you get a new word:
jô -> ju (cf. jostan), jâ
dô (cf. davidan) -> do (2), di (yesterday)