"Το ζουζούνι πίνει νερό."

[J.C.M.H.]

νερό is so different from Ancient Greek ὕδωρ! I did not think that the forms of words so basic in Modern Greek would be so different from Classical Greek.

[troll1995]

Yes, it comes from the koine phrase "νηρόν ὕδωρ" which means "fresh water". ὕδωρ is still used in other words that relate to water. Π.χ. υδατικός=aqueous, υδραυλικός=plumber etc

[J.C.M.H.]

Thanks for the explanation.

[jungerstein]

However, basic words are more likely to change because almost everyone uses them everyday. The long, complex, "ink-bottle" words resist changes more.

[Iva.Pelakova]

Is the word πίνει in infinitive like this? Or is it just 3. person? Does it change?

[troll1995]

It's just third person. Infinitive does not exist in modern Greek. Instead, subjunctive is used.

[FrancescaMamlin]

Why does water not have a definite article when other words would have one in this situation?

[kpagcha]

I bet the word for "to drink" in Greek and in Slavic languages are related (i.e. пить in Russian or pić in Polish).

[Gerasimos2522]

Fly more than bug says a native speaker