To 'ruin' something means to destroy or sabotage something. The verb 'to ruin' can mean to reduce something such as a building into a state of collapse, decay or disrepair. As a noun, a 'ruin' refers to a building that is disintegrating or is in a state of disrepair.

1. John hoped that his recent argument with his boss would not ruin his chances of promotion.
2. The scandal ruined the politician's reputation and led to his immediate resignation.
3. They decided to renovate the old house to stop it from falling into ruin.
4. We went to visit the castle but there wasn't much left of it. It was just an old ruin.

1. Pollution from the factory is ruining the surrounding countryside.
2. If my investments don't start doing better soon I'll be financially ruined!