Sun and moon letters


In Arabic and Maltese, the consonants are divided into two groups, called the sun letters or solar letters and moon letters or lunar letters, based on whether they assimilate the letter lām of a preceding Arabic definite article al-, which is an important general rule used in Arabic grammar. Phonetically, sun letters are ones pronounced as coronal consonants, and moon letters are ones pronounced as other consonants.
These names come from the fact that the word for 'the sun', al-shams, pronounced ash-shams, assimilates the lām, while the word for 'the moon', al-qamar, does not.

Rule

When followed by a sun letter, the of the Arabic definite article al- assimilates to the initial consonant of the following noun, resulting in a doubled consonant. For example, for "the Nile", one does not say al-Nīl, but an-Nīl.
When the Arabic definite article is followed by a moon letter, no assimilation takes place.
The sun letters represent the coronal consonants according to the phonology of Classical Arabic, and the moon letters represent all others. The sun and moon letters are as follows:

Jīm

The letter Gimel jīm is pronounced differently depending on the region of the speaker. In many regions it represents a coronal consonant such as or. However, in Classical Arabic, it represented a palatalized voiced velar plosive or a voiced palatal plosive . As a result, it was classified as a moon letter and it never assimilates the article. Maltese ġ is also considered a moon consonant while its voiceless counterpart ċ is a sun consonant.

Maltese

The sun and moon letters are as follows:
If a word starts with any of the moon letters, the definite article il- stays the same and does not assimilate, while with the sun letters it assimilates accordingly to to: iċ-, id-, in-, ir-, is-, it-, ix-, iż-, iz-. It is also worth mentioning that words starting with vowels, and the letters għ, and h get the definite article l-. When the definite article comes exactly after a word ending in a vowel, the initial of the article always drops, as in "dak ir-raġel ra r-raġel". When a word starts with two consonants, the definite article used is l-, but an i is attached at the beginning of the word: skola > l-iskola and Żvezja > l-Iżvezja.

Orthography

In the written language, the ال al- is retained regardless of how it is pronounced. When full diacritics are used, assimilation may be expressed by putting a shaddah on the consonant after the lām. Non-assimilation may be expressed by placing a sukūn over the lām.
Most modern-written Arabic names do not follow the consonant assimilation rule or the shaddah when latinized in Latin-spelled languages. Sometimes the sun and moon rules are not followed in casual speech.
E.g. personal name: الرَّحْمَن - Al-Rahman instead of "Ar-Raḥmān";
geographical name: الْجُمْهُورِيَّةُ التُّونِسِيَّة - Al-Jumhuriyah Al-Tunisiyah instead of "al-Jumhūrīyatu ’t-Tūnisīyah".