Conditional sentences contain two clauses: a subordinate clause (usually starting with if, when, or unless) and an independent clause. The subordinate clause (sometimes called the if or unless clause) states the condition or cause; the independent clause states the result or effect.
Verbs in conditional sentences do not express the time of an action in the way that verbs usually do. Rather, the present tenses typically express factual or true conditions, and past tenses typically express speculative or imaginary conditions.
Three kinds of conditional sentences are discussed in this section: factual, predictive, and speculative.
Exercise:
Verbs in conditional sentences