ruin :
is: the state of being severely
damaged or spoiled, or the process
of reaching this state...7
if something is in ruins, it is completely spoiled.
EG...a civilization that was
in ruin
to ruin: to ruin
something means to severely damage or spoil it. EG
you are ruining your health...villages had been burned
and ruined...
excerpts from the Collins-Cobuild
English Language Dictionary