"He is an atheist."
Translation:On jest ateistą.
Shouldn't it be "On jest ateistem"? Why is it the female decl, does this work similar to mężczyzna?
"On jest ateistem" would work if the Nominative was "ateist", but it is not.
"ateista" is indeed one of those words that are masculine despite looking feminine, like mężczyzna, tata, poeta, turysta etc.
The feminine word is "ateistka", so "Ona jest ateistką".
Nie ma za co :)
It should be "Wspaniale!", the adverb. Why? Well, it's just an exclamation, there is no noun to be described by the adjective (the masculine adjective) that you used. This is something clearly confusing to the learners and I'm afraid difficult to explain... Basically, if you hear some good news and you say "That's great!", it doesn't exactly have any subject. Not from the point of view of Polish, at least. That's why you use an adverb.
Hmm... it can seem like that, but not really, I think. For example you will not say "Fantastically!" to say that you are very happy with something. Similarly, let's say you're the boss and your employee reports to you and they say that everything is on track. You will rather answer "Good!" than "Well!". But in Polish, that will be the adverb "Dobrze!".