the phrase "a day" in English should also include the translation "κάθε μέρα" in this example, or no?
Given that there is better word-for-word matching I'd say no. In this context, I do this:
per day = ανά ημέρα
a day = τη μέρα / την ημέρα
every day = κάθε μέρα
I agree. In this context doesn't suit to use κάθε μέρα.
Ο εργαζόμενος τρώει δύο αυγά την ημέρα. it is correct
why is wrong "Ο εργάτης τρώει δύο αβγα τη μέρα
It's correct and added now as a possible translation. Thanks