There are three types of “ال” in Arabic Grammar: “ ال العهدية” which shows that you are talking about something known as in this âya from Holy Quran (الرسول) {إنا أرسلنا إليكم رسولا شاهدا عليكم كما أرسلنا إلى فرعون رسولا فعصى فرعون الرسول} [المزمل: 15 - 16] This "al" gives to the word the meaning of the prophet that I mentioned before and you have learned about him. This type of “al” is three kinds; العهد الذكري which I’ve given an example for it, العهد الذهني and العهد الحضوري. No need to say more in order not to make the topic longer. In short this type of “al” is for defining as you have learned in your studying of Arabic. The other type is “الجنسية”. This type of “al” is also two kinds; “للاستغراق” and “لتعريف الحقيقة”. “al” in your examples is this kind of "al". This "al" gives the meaning of containment of all individual as in this verse: {وخلق الإنسان ضعيفا} [النساء: 28] That means, all human being was created weak. الشّبابُ أَمَلُ الأُمَّةِ All and every young person. الحِكْمَةُ ضالَّةُ المُؤْمِنِ All and every kind of hikme. There are third type of al. Which is الزائدة. No need to talk about it as an answer to your question. In short ال الجنسية not only gives the definiation meaning but also gives the meaning of inclusion of all individuals. If it’s said شباب أمل الأمة without "al", an arab would think which young you are talking about? And wouldn’t understand your purpose. But when you say it with "al", he’ll understand that you mean all the youngs right away. Sorry for bad English Wesselam.

I'm trying to help but I don't understand what is your question

Arabic grammar is quite challenging, but it's OK for me. Thanks anyone. I hope you don't get tired of my questions :D

Hi, I think that Bana's answer is clear, and we can't ask why it's used for general statements too, because we're talking about the nature of Arabic. And I think it's the same use of definite nouns for French and English.

Thanks Bana.