But and If

But adverb - And nothing more.

If is a synonym for but. In some cases you can use "If" instead the word "But" as a conjunction or a noun.

If noun - Something taken as being true or factual and used as a starting point for a course of action or reasoning.

But is a synonym for if in though topic. You can use "But" instead the word "If" as a conjunction or a noun, if it concerns topics such as although.