A school in London has banned slang in the classroom to try improve the way the students speak.
Harris Academy Upper Norwood School in Croydon wants kids to stop using words like 'ain't', 'coz' and 'innit' because they think it will improve education standards.
Other people say slang is just an example of how language is developing.
But if you're a bit confused about what the latest slang terms mean never fear. From 'sick' to 'rank', or 'mint' to 'minging' these kids in Manchester have told Newsround some of the most popular words and what they mean.
Watch the video and see how many you know.
Use your new knowledge to take our