Here's why:
* Connects words, phrases, or clauses: It joins two parts of a sentence together.
* Shows contrast or opposition: It often introduces a contrasting idea or thought.
* Can be used in different ways: It can be used to show a contrast between two things, or to introduce an unexpected outcome.
Examples:
* I wanted to go to the party, but I was too tired. (Connects two clauses, showing contrast)
* The weather was beautiful, but I stayed inside. (Connects two phrases, showing contrast)
* I tried to call you, but you didn't answer. (Connects two clauses, showing unexpected outcome)