4 Sun letters

As you have learned, the definite article is ال (al-).

kitaab   > al-kitaab

walad  > al-walad

jaami3a > al-gaami3a

There is one more nuance to this that does not affect spelling, but does appreciate pronunication.  This is that all letters that make a “t” “s” “sh” “z” “r” or similar sounds (splosives

prounounced in the front of the mouth)  are considered “sun letters.”  When you add an ال to words that begin with one of these letters, the ل  (L) is silent, and you double the sound of the first letter.  Thus

to say hello the word “Salaam” has an ال on it, but you do not pronounce al-Salaam but instead as-Salaam (with the initial “s” standing in for the “l” that was elided.)

salaam > as-salaam

Taalib > aT-Taalib

rabb > ar-rabb

Zarf > az-Zarf

You will review these sun letters more later after you have learned the entire alphabet, but we wanted to introduce this to you know to aid your correct pronunciation.