Vinnfred, does someone "own" a temperature if they are asked if they have one? :)D
Later in the lesson, we are asked to translate "Do you have a temperature?." The correct responses are "У тебе є температура?" and "У вас є температура?."
Please help me understand the difference.
There no real rules, you know. So I just say what I feel is right :D
If you want to ask about someone's temperature, you may use both questions (with or without є). But with є it sounds like you don't know whether or not the person has a temperature, without є: you suspect that he does have it and just want to be sure.
But we don't really say є in the affirmative
So far I've heard confusing comments...
For example, there was a comment by @Vinnfred and also another contributor saying "У мене є температура" or "У мене є гарячка" is unnatural; however, asking someone else, "У вас є температура?" sounds OK. To me it still sound strange, because it sounds like you "own" it, rather than just have it, just like @Vinnfred said.
Then, "Я маю температуру" or "Ти маєш температуру". To me both sound unnatural since, again, "маєш" implies possession. However, I come from a region where the usage of "Я маю" is very uncommon in any situation, so my perception of it could be different.
Currently I updated all exercises involving this topic to not have "є" in 1st person singular, have optional "є" in questions, and currently all of them include "маю/маєш".