Quote Originally Posted by heartfelty View Post
There was hostility in his actions.
Hostilities erupted between the Serbians and Croatians.
Look at how they evolve into nouns.
Thanks to all! You are doing me wonderful favours.
Don't make the mistake of expecting Russian translations to map perfectly onto English. "Hostility" has more than one definition, and "hostilities" is only the plural of one of them. Other senses of the word are uncountable nouns.

"Hostility" in the sense of a feeling of antagonism or enmity is враждебность
"Hostilities" in the sense of acts of warfare is something like военные действия