Language Learning

Sun Letters and Moon Letters

The Arabic letters are two categories: sun letters and moon letters. The definite article ال "the" triggers this classification. The ال precedes indefinite nouns and adjectives (i.e., attached to them to be exact). Basically, the ل in the ال assimilates to the certain subsequent letters. These letters are called sun letters. And it (the ل) does not assimilate to other letters. These are called moon letters.

Why does this assimilation happen? It happens because the points of articulation in the oral cavity (mouth) for the sun letters and the ل are adjacent. Therefore, the ل gets assimilated to the sun letter that follows it. The sun letter, in turn, becomes doubled (i.e., a geminate). This doubling is marked by shaddah  ّ on the sun letter. In phonology (the science of speech sounds), this kind of assimilation occurs because the ل and sun letters share many phonological features. As for writing, the ل of the definite article ال is not affected; that is, it is written. 

Why are they called sun letters? They are called sun letters after the word شَمْس "sun", which begins with the letter (sound) ش /sh/ to which the ل assimilates. This word (i.e., شَمْس) is chosen because it is one of kind. Also, it sharply contrast with the word قَمَر "moon." 

If you look at the Arabic diagram presented in a previous lesson, you will notice that the letters that are produced / articulated from the vicinity of the ل are:

ت ، ث ، د ، ذ ، ر ، ز ، س ، ش ، ص ، ض ، ط ، ظ ، ل ، ن

In the following table, you can see that the ل under the pronunciation column is dropped and replaced with shaddah over the subsequent letter (the sun letter). 

Likewise, the moon letters are named after the word قَمَر "moon" which begins with the letter (sound) ق. The word قَمْر sharply contrasts with the word شَمْس. Plus, it is one of a kind. Assimilation of the ل to the moon letters is impossible because their points of articulation is far from that of the ل. In other words, they do not share any phonological features with the ل. These letters are: 

 أ ، ب ، ج ، ح ، خ ، ع ، غ ، ف ، ق ، ك ، م ، و ، هـ ، ي

In the table below, you can see that the ل does not assimilate with the subsequent moon letter, as shown under the pronunciation column.