‘If’ usually introduces conditional clauses. The same applies to other conditionals such as unless, should and in case which, however, perform other functions in different contexts. As conditionals, ...

Conditional sentences express a connection between two actions or states. One thing happens because of another. These connections can be general, specific, likely, unlikely, real or imagined. Although ...

The most common mixed conditional combination is when we have a third conditional in the if-clause (if + past perfect) followed by a second conditional (would + infinitive) in the main clause. To ...