6•a. The most commonly used kind of phonemic change in the New Persian derivation is the insertion of a phoneme or a phoneme string into a formation, usually to facilitate pronunciation. Such a phoneme or phoneme string is called epenthesis (آوایِ ميانجی).

6•a•a. If the derivation causes the phoneme constellation /C₁C₂C₃ - VC₁C₂/ (having one of the vowels /ɒ - i - u/), this phoneme constellation can be changed into the forms /C₁C₂VC₃ - V₁C₁V₂C₂/, respectively, by means of a vowel.

• The vowel /e/ is normally used as an epenthesis:
  • Between prefix and affixial focus, for example /pɒresæng/ پارسنگ and /pɒdeʃɒh/ پادشاه
  • Between interfix and affixial focus, for example /ʃæb-ɒne-ruz/ شبانروز
  • In the Juxtaposition of Nouns with Present Participles, for example /ʃɒde-mɒn/ شادمان
• The lexeme /mehræbɒn/ مهربان has the epenthesis /æ/.
• If consonant /j/ is the final phoneme of the constellation /C₁C₂C₃/, the epenthesis /i/ is applied:

  /ʃæhr/ + /jɒr/ = /ʃæhrijɒr/ شهريار

6•a•b. Consonants are used as epentheses, when two vowels are placed directly after each other in the derivation:

• Epenthesis /g/ is considered in these cases:
  • 1•1•3•2•a•a. The Suffix /æk/
  • 1•1•3•19•a•a•b. The Suffix /ɒn/
  • 1•1•3•19•a•c. The Suffix /ɒn/
  • 1•1•3•48•a•a•a. The Suffix /i/
  • 1•1•3•48•b•a•a. The Suffix /i/
  • 1•1•3•50•a. The Suffix /in/
• Epenthesis /h/ is used in this case:
  • 1•2•3. The determinative flexive /e/
• Epenthesis /k/ is used in these cases:
  • 1•1•3•19•a•a•b. The Suffix /ɒn/
  • 1•1•3•19•a•c•b. The Suffix /ɒn/
  • 1•1•3•48•a•a•c. The Suffix /i/
• Epenthesis /v/ is used in this case:
  • 1•1•3•48•b•a•b. The Suffix /i/
• Epenthese /vv/ is used in this case:
  • 1•1•3•63•a. The Suffix /om/
• Consonant /j/ is an epenthesis in these cases:
  • 1•1•1•8•a•a. The Prefix /mæ/
  • 1•1•1•10•a•a. The Prefix /næ/
  • 1•1•3•1•a. The Suffixes /æ - e/
  • 1•1•3•2•a. The Suffix /æk/
  • 1•1•3•4•a. The Suffix /æm/
  • 1•1•3•5•a. The Suffix /æn/
  • 1•1•3•6•a. The Suffix /ænd/
  • 1•1•3•7•a. The Suffixes /ændæ - ænde - ændu/
  • 1•1•3•11•a. The Suffix /ɒ/
  • 1•1•3•19•a•a. The Suffix /ɒn/
  • 1•1•3•19•a•b•b. The Suffix /ɒn/
  • 1•1•3•21•a. The Suffix /ɒni/
  • 1•1•3•41•a. The Suffixes /eʃ - eʃn - iʃ/
  • 1•2•1•a. The formation flexive /e/
  • 1•2•1•b. The formation flexive /e/
  • 1•3•2•a. The Present Flexives /æm - æd - ænd/
  • 1•3•4•a. The Imperative Flexives /æm - æd - ænd/
  • 1•3•5•a. The Optative Flexives /ɒm - ɒd/
  • 1•3•6•a. The Potentialis Flexives /æmi - ædi - ændi/
• Epenthese /jj/ is used in these cases:
  • 1•1•3•63•a. The Suffix /om/
  • 1•2•1•a•c. The formation flexive /e/

6•a•c. In addition, the epenthesis /i/ is used also in the following cases:

• 1•1•3•19•a•d. The Suffix /ɒn/
• 1•1•3•20•a. The Suffixes /ɒnæ - ɒne/

6•b. Elision (حذفِ آوائی) is the omission of phoneme or a phoneme string. The elision appears in New Persian in the following processes:

• 1•1•1•4•a•b. The Prefix /be/
• 1•1•1•4•a•c. The Prefix /be/
• 1•1•1•4•a•d. The Prefix /be/
• 1•1•1•4•a•e. The Prefix /be/
• 1•1•1•4•a•f. The Prefix /be/
• 1•1•1•8•a•a•b. The Prefix /mæ/
• 1•1•1•8•a•b. The Prefix /mæ/
• 1•1•1•8•a•c. The Prefix /mæ/
• 1•1•1•8•a•d. The Prefix /mæ/
• 1•1•1•8•a•e. The Prefix /mæ/
• 1•1•1•8•a•f. The Prefix /mæ/
• 1•1•1•10•a•a•c. The Prefixes /næ - nɒ/
• 1•1•1•10•a•b. The Prefix /næ/
• 1•1•1•10•a•c. The Prefix /næ/
• 1•1•1•10•a•d. The Prefix /næ/
• 1•1•1•10•a•e. The Prefix /næ/
• 1•1•1•10•a•f. The Prefix /næ/
• 1•1•1•10•a•g. The Prefix /næ/
• 1•1•1•10•a•i. The Prefixes /næ - nɒ/
• 1•1•3•8•a. The Suffixes /ængi - nængi/
• 1•1•3•19•a•c•c. The Suffix /ɒn/
• 1•1•3•40•a•a. The Suffix /estɒn/
• 1•1•3•40•a•b. The Suffix /estɒn/
• 1•1•3•44•a. The Suffix /gɒn/
• 1•1•3•45•a. The Suffixes /gɒnæ - gɒne/
• 1•1•3•50•a•a. The Suffix /in/
• 1•2•1•a•b. The formation flexive /e/

6•c. Anticipative dissimilation (ناهمگون‌سازیِ آوائی) is considered in the New Persian derivation only for vowels. In this case, a vowel becomes less similar to the next one. This is the case in the following processes:

• 1•1•1•4•a•a. The Prefix /be/
• 1•1•1•4•a•h. The Prefix /be/
• 1•1•1•4•a•i. The Prefix /be/
• 1•1•1•10•a•a•b. The Prefix /næ/
• 1•1•1•10•a•j. The Prefix /næ/
• 1•1•3•48•b•a•b. The Suffix /i/

6•d. Perseverative assimilation (همگون‌سازیِ آوائی) is a process, to match the distinctiven properties of a phoneme to the phoneme at its front. In the New Persian derivation, the perseverative is consided in the following cases:

• Conversion of the voiceless consonant /t/ to the voiced consonant /d/ after other voiced consonants or after vowels:
  • 1•1•3•65•a. The Suffix /t/
  • 1•1•3•66•a. The Suffix /tæn/
  • 1•1•3•68•a. The Suffix /tɒr/
• 1•1•3•48•a•b. The Suffixes /eʃ - eʃn/

6•e. Metathesis (قلبِ آوائی) is a sound change that alters the order of phonemes in a lexeme. It can be considered in the New Persian derivation in these cases:

• 1•1•1•4•a•e. The Prefix /be/
• 1•1•1•4•a•g. The Prefix /be/
• 1•1•3•40•a•c. The Suffix /estɒn/

6•f. The process of building of diphthongs from monophthongs in the derivation is called diphthongization (مرکّب‌سازیِ واکه). It is used in the New Persian derivation for example in the following cases:

• 1•1•1•10•a•i. The Prefixes /næ - nɒ/

6•g. The conversion of diphthongs to monophthongs is called monophthongization (ساده‌سازیِ واکه). Monophthongization is considered in the New Persian derivation for example in the following cases:

• 1•1•1•10•a•h. The Prefixes /næ - nɒ/
• /bu/ + /estɒn/ = /bostɒn/ بستان

6•h. The term combinative variation (چندآوائیِ مشروط) describes the case, when a phoneme accepts different phones (= allophones, واج‌گونه), depending on the surrounding phonems.

In the archaic New Persian (until the Mongolian era), the phoneme /d/ د is exchanges into the allophone /ð/ ذ, when it is placed after a vowel (see 1•1•1•3., 1•1•3•12., 1•1•3•34., 1•1•3•37., 1•1•3•38., 1•1•3•65•a., 1•1•3•66•a. and 1•1•3•68•a.).

There is no combinative variation in the modern New Persian. The allophone /ð/ ذ appears generally as phoneme /d/ د. Few evidences have kept the diction ذ, but with the pronunciation /z/:

پذيرفتن /pæziroftæn/، گذشت /gozæʃt/