Questions & Answers about هل الكتاب جيد؟
Why does الكتاب have ال (the) but جيد doesn't?
This is how Arabic makes a nominal sentence (a sentence without a verb). The subject الكتاب is definite because it has ال (the), while the describing word جيد (good) is indefinite and has no ال. If both had ال, it would just be a phrase meaning "the good book" instead of a full sentence.
Where is the word for "is" in this sentence?
Arabic does not use a word for "is" or "are" in the present tense. You simply put the subject الكتاب right next to the adjective جيد to create the meaning "the book is good".
How does هل work here? Does it change the sentence structure?
هل is a simple question word used to ask yes/no questions. It just sits at the very beginning of the sentence and does not change the word order at all. The phrase الكتاب جيد means "The book is good", and putting هل in front simply turns it into "Is the book good?".
Why is it جيد and not جيدة?
Adjectives always have to match the gender of the noun they describe. Because الكتاب is a masculine noun, we use the masculine form جيد. If we were asking about a feminine noun like a picture (صورة), we would use the feminine form and say هل الصورة جيدة؟.