The basic pronunciation of ευ is "ev".
But before voiceless consonants, there is voicing assimilation and so it turns to "ef".
So e.g. Εύβοια is "evia" and ευρύς is "evris", but ευτυχής is "eftihis" and ευχαριστώ is "efharisto".
Consonants that are pronounced without your vocal cords vibrating.
Put your hand against the front of your neck and say "fffffff". Keep your hand there and say "vvvvvv".
When you say "vvvv", you should feel your vocal cords vibrating. When you say "fffff", they do not vibrate.
Voiceless sounds are sounds like "f", where the vocal cords do not vibrate -- others are "p t k f θ χ s".
Voices consonants include "b d g v δ γ z m n l r".
Many consonants come in pairs (one voiceless, one voiced), e.g. p/b.
Some do not have a "partner", though; for example, there's no voiceless "m" sound in Greek.
Slowly, slowly. Don't worry about the grammar...rules, etc. Just learn the sentences as you go on.
ASk quesitons whenever you want anything explained.
Any relation with the ethymology of Oxygen or Oxide?
Nope; those are related to οξύς with a xi (ξ) -- this word has a chi (χ). It's not ochigen :)
"No, thank you" is certainly correct and should have been accepted. Where did you encounter it? On the web, Android or iOS?
We also accept "No, thanks!" as correct. Why do you consider it wrong?
Im just happy im learning greek finally i meana greek going 15 years without knowing his language
Welcome aboard and happy learning. Let us know if we can help with anything.
The Greek team has no way of seeing anything that learners write so we can't tell you if it's correct or why it was rejected. The execises are graded by the computer program. We have never had a perfect answer reject so there might have been a small error you didn't notice. Why don't you tell us what the exercise was, exactly what you answered, and what the response to your answer was?