This is the 577th most frequent Greek word.
νερού
The Greek word "νερού" means "of water" or "water's" (possessive form).
In this sentence, 'νερού' is a genitive case denoting possession or specific content (a glass of water).
Θα ήθελα ένα ποτήρι νερού, παρακαλώ.
I would like a glass of water, please.
Here, 'νερού' is again in genitive case, describing the characteristic ('taste') belonging to 'water'.
Η γεύση του νερού είναι αναζωογονητική.
The taste of the water is refreshing.
In this case, 'νερού' is used genitively to express the origin or source of 'power' (from water).