Assimilation Rules (Idghām & Morphological Assimilation)

Assimilation occurs when two consonants come together in such a way that the first absorbs into the second, creating doubling (shaddah) or sound transformation. ACE applies these rules when generating Arabic script.

1. Form VIII Assimilation (اِفْتَعَلَ → اِدَّعَى etc.)

When the prefix تْ (ta) of Form VIII meets the first radical, it may assimilate:

• d, z: ت becomes د
  اِدَّكَرَ ← *اِتْذَكَرَ
• ذ: both become doubled دّ
• ت: merged into تّ
• ṣ, ḍ, ṭ: ت becomes ط
• th, ẓ: full assimilation into a doubled consonant
• w: the و drops and assimilation forms اِتَّ...

2. Nun Assimilation (Idghām)

When نْ encounters certain letters, it merges and is replaced by shaddah.

3. Lam Shamsiyyah

The ل in “al-” assimilates into sun letters (t, th, d, dh, r, z, s, sh, ṣ, ḍ, ṭ, ẓ, n, l).

4. Hamza Assimilation (Seat Change)

• After ā (aA): ء becomes standalone (ء)
• After ū (uw): hamza sits on و (ؤ)
• After ī (iy): hamza sits on ي (ئ)

ACE applies these rules automatically during Latin→Arabic conversion.