Conditional sentence

A conditional sentence is a sentence in a natural language that expresses that one thing is contingent on another, e.g., "If it rains, the picnic will be cancelled." They are so called because the impact of the sentence’s main clause is conditional on a subordinate clause. A full conditional thus contains two clauses: the subordinate clause, called the antecedent (or protasis or if-clause), which expresses the condition, and the main clause, called the consequent (or apodosis or then-clause) expressing the result.

To form conditional sentences, languages use a variety of grammatical forms and constructions. The forms of verbs used in the antecedent and consequent are often subject to particular rules as regards their tense, aspect, and mood. Many languages have a specialized type of verb form called the conditional mood – broadly equivalent in meaning to the English "would (do something)" – for use in some types of conditional sentences.