Sun and Moon Letters (حورف شمسية و قمرية)

In Arabic, - ا ل pronounced al-, is the definite article, like the word "the" in English, and it is attached to the front of the word. Example:

كروسي

"kuursii"

chair

vs

ال كروس ي

"alkuursii"

the chair

The human tongue is inherently lazy; looking for the quickest, easiest way to pronounce things. The evidence of that in this case, is that the the laam ل when attached to words as part of - ا ل , is sometimes assimilated to the letter following it because it is quicker and easier than fully articulating it. The letters that assimilate the Laam, ل , are called Sun Letters. This is because the word for sun, شمس (shams) assimilates the alif laam, - ا ل . The Sun letters are as follows:
ت ث د ذر ز س ش ص ض ط ظ ل ن What does it mean to assimilate? It means that instead of pronouncing the , ل laam, L-sound, the first consonant of the word gets doubled. So, for the word Sun : شمس

شمس

shams

sun

becomes

الشّمس

asshham s

the sun

Here are a few more examples:

دجاج	dajaaj	chicken	becomes	الدّجاج	addajaaj	the chicken
طفل	Taful	child	becomes	الطّفل	aTTaful	the child
رجل	rajal	man	becomes	الرّجل	arrajal	the man

Note the appearance of a symbol above the words in the fourth column,ّ . This symbol is called a shaadda and appears above a consonant to indicate that it is a doubled consonant. They are not restricted to just this usage, in the case of the assimilated - ا ل , but are found throughout the Arabic language.

The Moon Letters جورف قرمية (Haruuf qamriiya) are all of the remaining letters. They DO NOT assimilate the ل , laam, L-sound and everything is pronounced as expected. They are called Moon Letters جورف قرمية (Haruuf qamriiya) because the word for moon, قمر , (qamr) does NOT assimilate. Here they are below:

أ ب ج ح خ ع غ ف ق ك م ن ه و ي