This article deals with such a phenomenon in Modern British English as slang, also there are adduced the reasons and motives for it. A definition of the term "slang" is given. The relevance and importance of slang in modern language is explained. A brief explanation of the main characteristic of slang is given. Different slang expressions and explanation are given with the aid of particular examples of using slang expressions in speech. The presence of rhyming slang in Modern Brittish English is explained. A description of rhyming slang and its examples are given. Shortened variants of rhyming slang are described and explained. A conclusion is made on the importance of acknowledging such a phenomenon as slang words. The relevance and importance of slang in Modern British English is confirmed.