1. As a conjunction:
* To introduce a contrasting idea: This is the most common use. "But" indicates that what follows is different from or opposed to what came before.
* *Example:* "I wanted to go to the party, but I had to work late."
* To introduce an exception: It can also be used to show that something is true in most cases, but not in all cases.
* *Example:* "Everyone loves pizza, but my brother hates it."
2. As a preposition:
* To mean "except": "But" can be used to indicate that something is excluded.
* *Example:* "Everyone was invited to the party but me."
3. As an interjection:
* To express surprise or doubt: "But" can be used alone to express surprise, disbelief, or uncertainty.
* *Example:* "But, that's impossible!"
4. As a noun:
* In the phrase "the buts": This phrase refers to objections or concerns.
* *Example:* "We have to consider the buts before making a decision."
Ultimately, the definition of "but" depends on how it is used in a particular sentence.