"عِنْد روزا جاكيت."
Translation:Rosa has a jacket.
The circle is there to show that there is no vowel sound after the ذ.
And now I have my own follow up question for those more familiar with Arabic than me. I know the diacritics are often left out of writing; is the ْ also commonly left out? I ask because, thinking about it, in a world where you could have either مَسَك or مَسْك, you either use diacritics and could just as easily assume that there's no vowel sound after the س because it lacks a vowel diacritic, or not use diacritics and have ْ mark where not to put a vowel sound, assuming that a vowel would be said there if there was no ْ. I'm sure in either case, you'd just figure it from context anyway, I'm just trying to paint a fuller picture of the use case of ْ.
Well, I suggest you go to some Arab news website like www.aljazeera.net and see for yourself :-) Can you find any ْ (sukūn)? It is usually being omitted like all other diacritics. There are very rare exceptions - for example when it comes to the active/passive form of a verb.
So basically, to understand, to read and to pronounce a text in Arabic correctly you have to know the words (including their vowels). After some time you will start to recognize certain "patterns" and automatically pronounce them correctly.
Example: maybe you already learned the word ٌشَمْس (sun). The adjective is مُشْمِسٌ (sunny). In another context you read ممطر (without diacritics) and you will recognize the root مَطَرٌ (rain). So you can guess that ممطر means "rainy" and is pronounced مُمْطِرٌ (like مُشْمِسٌ). Same for verbs. Those "forms" are not random - they are a crucial part of the Arab grammar (and they make Arabic a very systematic language).
But to be honest, I doubt that it's possible to learn all this by just using a software like Duolingo. However it's a good start :-)
As a Hebrew speaker, and Hebrew being a 'sister' language to Arabic (they're both semitic languages with similar gramatical rules, many similar words etc.) I can say that we know by context how to prnounce a word without diacritics (we have different looking letters and diacritics, but the concept is the same).
Sometimes newspapers /written texts add diacritics to a specific word if it's a foreign word or if its meaning is ambiguous.
Unfortunately, you do hear "name butcherings" and mispronunciations of non-familiar names and words so often, because of the lack of diacritics.
And even if they are present, some native speakers don't even remember how to read them (at least in Hebrew) since they were taught these symbols as kids when learned to read/write, and since then haven't used them.