Solar and lunar letters

Consonants witch assimilate or do not assimilate the lâm of the article

In arabic, there are two different types of consonants :

Solar letters :

ت ث د ذ ر ز س ش ص ض ط ظ ل ن
The word شمس (sun) following the article الـ is written الشمس and pronounced ash-shams. The lâm of the article is assimilated and the shîn twice so. The consonants which assimilate the lâm of the article are called : solar letters حروف شمسية with regards of the first letter of the word شمس. All of them are coronal letters, namely letters which involve using the tip of the tongue.

Lunar letters :

ء ب ج ح خ ع غ ف ق أ ك م ه و ي
The word قمر (moon) following the article الـ is written القمر and pronounced al-qamar. The lâm of the article is voiced. The consonants which do not assimilate the lâm of the article are called : lunar letters with regards of the first letter of the word qamar.