Conditional sentences are composed of two clauses: a condition clause introduced by "if" and a consequence clause. There are three main types of conditional patterns: the first conditional expresses probable conditions using present tense in the if-clause and future tense in the consequence clause. The second conditional expresses improbable conditions using past tense in the if-clause and "would/should/could" verbs in the consequence clause. The third conditional expresses imaginary conditions not seen in the present using past tense in both clauses.

1. Conditional Sentences by miguel ángel rodríguez lópez