Translation:The team has five thousand fans.
We had started doing it, but then we stopped, because we considered that most learners would use the numbers instead of their Greek names. Plus, in a formal text you have to write the numbers in Greek (except big numbers) and you also know how to use the numbers. There is no need to teach this ;)
Curious - it accepts "5 thousand" but not 5000. Incidentally in English it is generally accepted practice to write out the words for numbers 1-9, but use numerals above this - I don't know whether it is the same in Greece.
I understand the desire to encourage people to learn the words for numbers- but I am learning Greek not English, so having numerals in English is convenient.
ὀπαδός is ancient Greek for a follower (ὀπηδός), one who does the same as a predecessor. Since it also had the sense of an attendant, one can see how ὀπαδός in the sense of a follower or attendant could relate to being a fan (e.g., one who attends, one who follows). φιλάθλους is such a great word and needs less explanation. I'll just note that it's also ancient Gk and more or less referred to a competitor who was fond of competing in games. It makes sense that it still refers to someone who loves athletic competition. Dimitra (moderator) helps with modern Greek here: https://forum.duolingo.com/comment/18998063