"The vegetarian eats a potato."
Translation:Ο χορτοφάγος τρώει μία πατάτα.
ένα μια...are all wrapped up in the subject of genderes. If English is your native language you are only exposed to genders with in a few cases...for example "he" for males, "she" for "females etc. It's all clear and simple.
In Greek all nouns have genders and IT REFERS TO THE GENDER OF THE WORD NOT THE PERSON OR THING. And there is not set rule for what will be masculine, feminine or neuter...
In order to see more about this you should be reading the "Tips & notes* for each Skill starting with the Basic....
This will give you a picture of how we use genders...."ένα, μια, ...." etc "ο" "η " "το"
And to find out where you use each follow these tips....
TIPS TO MAKE LEARNING EASIER and EFFECTIVE + HOW TO REPORT A PROBLEM
they will help you:
1 always find the correct translation (Drop Down Hints)
2 find explanations for grammar and vocabulary....(Tips & notes)
3 Show you what to do if your sentence is rejected or you have another problem.
Also, check out the Greek Forum with many more resources…... https://forum.duolingo.com/topic/936