vice
n. C / U C1 Advanced Oxford US //ˈvaɪs// vice
n. a bad habit or a moral weakness in someone's character. It is often used to talk about things like smoking or gambling that are hard to stop.
n. a moral failing or a persistent wicked habit. Often used to refer specifically to activities involving illegal or immoral conduct, such as gambling or narcotics.
My only vice is eating too much chocolate.
The city established a special police unit to investigate crimes related to vice and illegal gambling.
The protagonist's tragic downfall was not caused by a single grand mistake, but by a collection of small vices that slowly eroded his professional reputation.
Usage
Countable when referring to specific habits; uncountable when referring to the general concept of immoral behavior.