The Definite Article: ال Meets ה־

Arabic has exactly one article: ال (al-), glued to the front of the noun. There is no word for "a/an" — a bare noun is simply indefinite. If you are thinking "that is precisely how ה־ works in Hebrew", you have already finished half this lesson.

Sun letters: the article that melts

Before roughly half the alphabet, the ل of ال assimilates: you write الشَّمْس but say ash-shams, not al-shams — the ل melts into the next letter, which doubles. The letters that do this are called sun letters (because شَمْس is the mascot); the rest are moon letters (mascot: قَمَر, moon), and after them ال stays crisp: الْقَمَر, al-qamar. The sun letters are exactly the ones made near the tip of the tongue, where ل itself lives: ت ث د ذ ر ز س ش ص ض ط ظ ل ن.

Definiteness agreement: הבית הגדול

In Arabic, as in Hebrew, the adjective follows its noun and must match its definiteness. An indefinite noun takes a bare adjective; a definite noun demands the article on the adjective too. The structures align word for word: בית גדול ↔ بَيْت كَبِير, הבית הגדול ↔ الْبَيْت الْكَبِير. If you can build Hebrew noun phrases, you can already build Arabic ones.