In Arabic, letters (or more accurately phonemes) are categroised into two categories: Sun letter and Moon letter in regard to what happen if we add Al (the) to them.

Moon letters don't cause any change to the word's pronunciation. For example, Al-Qamar (the moon) is actually pronounced how it is written. However, in the case of a word like Al-Shams (the sun) the l is not pronounced and the consonant sh becomes a doubled consonant (pronounced twice).

I was wondering about the phonetic reason for that phenomenon. What makes a native speaker of Arabic do this? Are some letters faster to pronounce twice rather than pronouncing an L before them instead? Or is that due to another reason?

3 Answers 3


The sun letters in Arabic are (or at least were in early Arabic) coronal consonants: t, d, ṭ, s, z etc., pronounced with the front part of the tongue touching the teeth or the roof of the mouth. In many styles of modern Arabic ج is also a coronal [dʒ], but in ancient Arabic it was probably more like [gʸ]; hence it is not a sun letter.

To describe this phenomenon as “assimilation” is not entirely correct, as it affects only the article. For example, you say at-tīn (with apparent assimilation of /lt/ > /tt/), but you also say iltizām, without assimilation of the same cluster. So it is not a purely phonological thing, but one that is morphologically conditioned. In other words: /lt/ is assimilated if /l/ is part of the article, but not assimilated if the /t/ is part of the reflexive infix in verbal morphology.

Similarly, there is no assimilation if the /l/ and the following letter if both are part of the root. E.g., you say as-sana (“the year”), but ʼalsina (plural of lisān “tongue”).

  • 1
    An important piece of the puzzle is that [l] is itself coronal; assimilation often works this way, starting with two sounds that are already somewhat similar and making them more similar.
    – TKR
    Commented Apr 15, 2016 at 18:29
  • @TKR: Yes, but what I am trying to say is that this "assimilation" is not a regular sound change, but is restricted to one single morpheme, the article. Thus, you are not going to find a purely phonological explanation for it.
    – fdb
    Commented Apr 15, 2016 at 18:43
  • Sure, I agree. Nevertheless it isn't random either: phonology and morphology are both needed to define it properly.
    – TKR
    Commented Apr 15, 2016 at 19:08
  • 2
    @fdb gives a good answer. But it's even more complicated. the /l/ in /iltazama/ may be sounded, but what about /inlazama/? Plus there are many examples in Quran and classical Arabic where assimilation crosses word boundaries. Plus, it's very likely that different dialects have always done things differently; remember that "Classical Arabic" is a fiction. What's fascinating is that Sibawayhi never attributed assimilation to rules, only to practice - "that's the way that Arabs talk", end of story.
    – mobileink
    Commented Apr 16, 2016 at 20:37
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    @Metamorphic. I meant a palatalised [g]. IPA should be [gʲ].
    – fdb
    Commented Jun 22, 2018 at 6:55

This is a assimilation process. When pronouncing words like : al-nar النار pronouncing it as /al nâr/ would be hard and thus they will pronounce it as /an nar/ these set of words are called coronal consonants meaning they are pronounced with the flexible front part of the tongue. In short it is done because it's easier to pronounce.

More on assimilation:

More on arabic phonology:

  • Al-Ani, S. H. (1970). Arabic phonology: An acoustical and physiological investigation (Vol. 61). Walter de Gruyter.

  • Brame, M. K. (1970). Arabic phonology: implications for phonological theory and historical Semitic (Doctoral dissertation, Massachusetts Institute of Technology).

  • Arabic Phonology and Script: An Introduction: University of Virginia, Oriental Languages, 1984 Writing, Arabic - 130 pages

  • 2
    If *al-tīn is “hard to pronounce” why is iltizām not hard to pronounce?
    – fdb
    Commented Apr 15, 2016 at 10:54
  • @fdb what is the second word? could you write the arabic word? /iltiznām/ Commented Apr 15, 2016 at 10:56
  • التزام ("Comments must be at least 15 characters in length" grrr)
    – fdb
    Commented Apr 15, 2016 at 10:59
  • 1
    @Adel Rahimi In Gulf Arabic, Al- is pronounced /ɪl/. Al-Tinnin (The dragon) is pronounce /ɪttɪnnin/, were in words that have /ɪl/ in the begining that is not the "the" /ɪl/ (in other words, the il is part of the word), the /l/ is pronounced, like in iltizam (commitment, /ɪltɪza:m/), which is strange considering that not pronouncing it would be easier according to the discussion.
    – Cyclone
    Commented Apr 16, 2016 at 6:35
  • 1
    I see. The unclear reason why assimilation doesn't always occur is really interesting, but I guess discussing that will be better in a new question, as the answer to the question posted here was already provided. Thank you very much for your answer and the article suggestions.
    – Cyclone
    Commented Apr 16, 2016 at 7:22

The general phonologic process behind that phenomenon is called assimilation. Ease of pronunciation is the usual explanation of this process, but note that assimilation is always language dependent and not predictable (e.g., latin octo became otto in Italian, but not in the other Romance languages).

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