This is slightly confusing in Arabic since it differs a lot from English. There are three different patterns you should be aware of... هَذَا كِتْابٌ = This is *a* book هَذَا الكِتَابُ = This book هَذَا هُوَ الكِتَابُ = This is *the* book They will become second nature as you practice with them. Don’t worry! بالتوفيق

السلام عليكم This word, هذا, can be used without the ال particle, but it carries a different meaning. When you want to say, "This x" you use ال. When you want to say, "This IS a(n) x", you do not use ال. For example: This book هذا الكتاب This is a book هذا كتاب In your examples, you would only need the prior. I hope this helps.

Unlike in English, where the definite article specifies only grammatical definiteness of the noun and does not affect the syntax, in the Semitic languages the role of the definite article is a mixture of several functions: 1) semantic function: reference to mentioned/known/understood nouns (the same as in the European languages); 2) syntactic function: an agreement in a nominal sentence and in genitive construct (idafa). The presence or absence of the article affects the syntax, i.e. changes the meaning of the sentence. 3) classifying function: the article acts as a mere noun marker distinguishing between nouns and other parts of speech (verbs, mostly). This functions might look unusual for European language speakers, since even though the noun takes the definite article, grammatically it remains indefinite. Basically, the second and third function has nothing to do with the concept of ''definiteness'' as European languages understand it.