Of perishable items, overridden with bacteria and other infectious agents.
"The rotten fruit had turned into a slimy mass that attracted flies within hours of being left on the counter."
In plain English: Rotten means something is so spoiled, damaged, or bad that it can no longer be used or trusted.
"The rotten apple fell from the tree and made a mess on the ground."
Usage: Use rotten to describe food or organic matter that has decayed due to bacterial growth rather than simply being old or dry. This term specifically implies a state of spoilage caused by infection, distinguishing it from non-perishables like furniture which can be damaged but not biologically rotted in the same way.
To an extreme degree.
"His behavior was rotten to the core, showing no hint of remorse or decency."
The word rotten comes from Middle English roten, which was borrowed from the Old Norse word rotinn meaning "decayed." This term ultimately traces back to the Proto-Germanic root *rutāną, also meaning "to rot."