Vowel Hiatus and Epenthesis

“Vowel hiatus” or “dieresis” refers to a sequence of two adjacent vowels that belong to separate syllables and there is no consonant sound between them. In some languages including Persian, the rules of how sounds are placed next to each other does not allow vowel hiatus. Persian resolves vowel hiatus by adding an extra consonant between adjacent vowels. This action is called “epenthesis” and the extra consonant is called an “epenthetic consonant”. The epenthetic consonant is often “y”, sometimes “ø” and in certain cases, “v” or “h”.

Persian’s syllable pattern is CV(C)(C). The following table shows all possible combinations for two adjacent syllables. In all cases, adjacent syllables never form “V-V”. This clearly proves that Persian disallows vowel hiatus.

Epenthesis in the interior of a word

There are two main spelling candidates for words like سیاه: “sîâh” and “sîyâh”. The first candidate breaks into the syllables ⟨sî-âh⟩ and the second candidate breaks into ⟨sî-yâh⟩. Given that Persian disallows vowel hiatus, only “sîyâh” is acceptable. In languages such as Spanish, it is possible to say “Espania” but in Persian, “es-pâ-nî-â” is not possible and this country is pronounced “Espânîyâ” (اسپانیا). More examples: “bîyâbân” (desert), “xîyâr” (cucumber), “pîyâz” (onion), “pâyîz” (fall, autumn).

In Arabic loanwords whose vowels are separated by a glottal stop, there is a tendency to replace glottal stop with the consonant “y”. For instance, رئیس is the original spelling but it is commonly written as رییس and is pronounced “ra-yîs” instead of “ra-øîs”.

Epenthesis at word boundaries

When a prefix ending in a vowel is added to a word beginning with a vowel, an epenthesis occurs. The epenthetic consonant is “ø” for the vowels “î” and “û” and for other vowels, a “y” is added. When the epenthetic consonant is “ø” (hamze, glottal stop), it does not appear in writing because in Persian, vowels at the beginning of a syllable are naturally articulated with a hamze, making it redundant to write “ø”. The following table shows some examples with the negation prefix “na-” and the imperfective prefix “mî-”.

When a suffix beginning with a vowel is added to a word ending in a vowel, an epenthesis occurs. The epenthetic consonant is either “y” or “ø”. When it is a glottal stop, it does not appear in writing. The following table shows “gû”, the present stem of the verb “goftan”, in combination with different suffixes.

Epenthesis between words

The English indefinite article “a” becomes “an” before a vowel. This is an example of epenthesis between words. The Spanish conjunction “y” (and) becomes “e” when it precedes a word that begins with the sound /i/. Persian has also examples of epenthesis between words.

The indefinite article “î” becomes “yî” after the vowels “â”, “o” and “û”.

The genitive marker “e” becomes “ye” after vowels.

The conjunction “o” (and) becomes “vo” after the vowel “â” and “yo” after the vowel “î”.

In spoken Persian, the dative preposition “به” (be) is combined with bound personal pronouns. The epenthetic consonant is “h” in this case.