I have noticed in previous exercises that some words have endings that are not written. In this case is the "-un" ending in the word "لُغة". Could someone explain this more detailed? Is it some kind of nominative case ending? What are the rules to it? What is it called (maybe I can research myself but don't know what to look for). I'd appreciate it.
Btw, this course is really good (I had previous knowledge on the writing system) and makes me quite happy to see it in Duo. I was waiting for it for a loooooong time.
It's the nominative indefinite ending, -un, which is rarely written, but if it were, it would be written as لُغةٌ
Notice how the small symbol above the ة at the end looks like two small وو linked together. That's what makes the -un sound. The grammar behind when we use what when talking about indefinite things is a bit too involved to explain here, so what I suggest you do is pay really close attention to what you hear while following the Arabic letters with your eyes, and you'll eventually get a feel of what to use when. It takes a long time to acquire this skill, so just be patient and listen to a lot of Arabic while following text every day. You'll get there eventually :-)
PS: We also often drop the sound when reading out loud (when that happens, ة isn't pronounced, which is another unrelated rule), so don't worry too much about it. If you really want to get it right all the time, you'd need to look for an Arabic grammar book, preferably one made for foreigners, because things can get quite involved, and you'd need to learn several concepts in a certain order to be able to understand everything.
To further elaborate on the method, I suggest you listen to Arabic recordings every day while following the letters with your eyes (So you'd need transcripts). Forget the meaning for now, just train your eyes to keep following the letters while noticing the sound being made. You'll find this a bit overwhelming at first, but give it 2 weeks of daily practice (10 minutes per day are enough) and you'll start feeling the benefits. Keep doing this throughout your learning, and the long term benefits will be immense, as you'd be much more familiar with the sounds of the language and its structure (unconsciously) and your brain will be a lot more ready to absorb the information once you get to it in the Duolingo tree (or using any other resource).
If you'd like general tips on learning languages, I recommend you read my previous posts on the subject, which you can find by following these links:
As for Arabic books, unfortunately, the availability of Arabic books (and good Arabic resources in general) online is rather scarce, and the best books about Arabic grammar tend to be written in Arabic, and only available at local bookstores in Arab countries. I've never had to learn Arabic as an adult (I'm a native speaker), so I can't judge the quality of grammar books made for foreigners. What I suggest you do is the same thing you'd do when buying any other book online: read Amazon reviews about the book. You'd probably need to buy more than one, as there is no perfect book. Some books explain certain aspects of the grammar better than others. In any case, if you're serious about mastering Arabic, you really need to look for an Arab friend asap so you have a way to check your pronunciation and understanding. Try to find one who is good in grammar. A lot of natives have forgotten grammar, because our dialects are completely different. And most importantly, have fun! :-)
As far as I know, you can actually say that the nunation (an,in,un) signifies indefinition of a noun, because definite nouns are preceded by the article ال .... (and they are followed by the sounds a,i,u.....without the n. The different vowel sounds signify different grammatical cases)
However this only happens within the flow of speech and, for example, not at the end of sentences. Generally, in most versions of spoken Arabic, it is completely omitted. Also, the definition or indefinition of adjacent adjectives can change the grammar of the whole sentence significantly.
Baitun kabirun = a big house Albaitu alkabiru = the big house Albaitu kabirun = the house is big
Btw, I have waited a long time for this course myself....had a little celebration. :)