The Definite Article

The definite article is اَلْ, written joined to the front of the word. It is the same for masculine and feminine. A noun that takes the article loses its tanwīn and keeps a single final vowel: بَيْتٌ baytun becomes اَلْبَيْتُ al-baytu, غُرْفَةٌ ghurfatun becomes اَلْغُرْفَةُ al-ghurfatu.

English a and an have no word of their own in Arabic. A noun ending in tanwīn is already a house, a door. The article and the tanwīn therefore never appear on the same word: a noun is either بَابٌ a door or اَلْبَابُ the door, never both at once.

An adjective comes after the noun it describes: بَيْتٌ كَبِيرٌ a big house, never the other way round. If the noun is definite, the adjective must be made definite as well, with its own اَلْ: اَلْبَيْتُ الْكَبِيرُ the big house. Both words carry the article, and both have lost their tanwīn. The adjective also keeps agreeing in gender, as you learned in lesson 14: اَلْغُرْفَةُ الْوَاسِعَةُ the spacious room.

Arabic has no word for is or are in a sentence like the house is big. The subject, usually definite, is simply followed by its predicate, usually indefinite: اَلْبَيْتُ كَبِيرٌ. You already used this pattern with pronouns (هُوَ كَبِيرٌ he is big); now the subject can be any noun with the article.

You know هٰذَا بَيْتٌ this is a house from lesson 12: an indefinite noun after هٰذَا forms a sentence. Put the article on the noun and the two words fuse into a single phrase: هٰذَا الْبَيْتُ this house, which now needs a predicate to become a sentence: هٰذَا الْبَيْتُ كَبِيرٌ this house is big. Add a definite adjective and the phrase grows: هٰذَا الْبَيْتُ الْكَبِيرُ this big house.