In answer to the question regarding عُس written as 3us in English
This is not a mistake; rather it is a style of writing popularly known as 'Arabizi' or 'Franco Arab', wherein, during transliteration, Arabic text is written using Latin numbers/characters that represent certain letters in Arabic.
Time (and space) does not permit me to go into depth regarding this culture, but to answer your question: The English transliteration of the Arabic letter ayn 'ع' is shown as the English numeral 3, due to the similarity in their written form, and also to eradicate confusion with the lighter hamza 'ء' which would be represented by the English numeral 2.
In example, '3rabizi' means 'عربيزي' (Arabizi), where the number 3 illustrates an ayn 'ع' in Arabic. Therefore, in Duolingo, the English transliteration of the Arabic word 'عُس' will be portrayed as '3us'.
I hope this helps, but I would suggest researching regarding this interesting phenomenon on the Internet, where you will be given more information.
HI THANK YOU SO MUCH FOR THIS! I'm new to learning Arabic and it really confused me why letters are mixed with numbers in one word, I kept thinking that my phone didn't support certain Arabic characters or something haha.
You explained really well, thank you for your time! X
P. S.. What websites would you recommend to read up on arabizi?
Hi, your comment made my day, thank you!
I don't really have any specific websites, just google and skim through links until you're satisfied.
Also don't worry too much about not understanding Arabizi, as it's not a very important aspect of learning the Arabic language, because it's more to do with transliteration into English. Besides, with practice on duolingo, hopefully you will get the hang of it in no time.
I personally find expressing the Arabic letters with numerals to be much clearer than if it were attempted with just the Latin script. Especially as ع and ء have no letter equivalent in English. It especially makes texting easy. I haven't encountered yet in Duolingo but the ones I have encountered on chat are:
(ح- 7) (خ – 5 or 7’) (ص- 9) (ض 9’) (ط - 6) (ظ – 6’) (ق – 8)