Here's why:
* Dialect refers to a variety of a language that is specific to a particular region or social group. It can differ from other varieties in terms of pronunciation, vocabulary, and grammar.
* Language is a broader term that encompasses all varieties and dialects.
* Slang is informal language used by a particular group of people. It is often temporary and changes over time.
* Idiom is a phrase or expression that has a figurative meaning that is different from the literal meaning of the words.
Let me know if you have any other questions!