"The door is a new and pretty door."
Translation:اَلْباب باب جَديد وَجَميل.
adjectives almost always come after the noun, but we have two cases:
1. Attributive: an adjective that describes the noun directly, and this adjective should mimic the noun it describes in all its features (gender, definition, number).
2. Predicative: these adjectives are telling the status (i.e. they might describe the noun but indirectly, in a form of a sentence).
To be in the line of the same sentence above, I will play with words below and give the translation:
1. Attributive: البابُ الجديدُ [albábu aljadídu] The new door. The adjective here followed the noun in singularity and in definition as well.
2. Predicative: البابُ جديدٌ [albábu jadídun] The door IS new. Here, we are informing the listener that the door is new. The adjective here (جديد: new) did not follow the noun (البابُ: the door) in definition. It is however a single form of the adjective. And because it is not defined with AL anymore, the Tanwin or nunation is placed at its end to mark it as indefinite adjective: جديدٌ.
There is a case when an adjective comes before the noun but it might be a bit advanced for now, but it has to do with superlative and comparative cases, and in specific speech style.
Thanks. Nominal sentences are interesting. I have a question: If the second element of the predicate is also definite, do we add the third person pronoun sometimes? That is my beginner understanding. http://www.llf.cnrs.fr/sites/llf.cnrs.fr/files/evenements/colloques/DG_copula.pdf