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.
Such sentences may be used to express a certainty, a universal statement, a law of science, etc.
(in these cases if may often be replaced by when): They can also be used for logical deductions about particular circumstances (which can be in various mixtures of past, present, and future): A predictive conditional sentence concerns a situation dependent on a hypothetical (but entirely possible) future event.
For instance, the "Anderson Case" has the characteristic grammatical form of a counterfactual conditional, but is in fact used as part of an argument for the truth of its antecedent.
[20] Languages have different rules concerning the grammatical structure of conditional sentences.
These may concern the syntactic structure of the antecedent and consequent clauses, as well as the forms of verbs used in them (particularly their tense and mood).
Conditional sentences in Latin are traditionally classified into three categories, based on grammatical structure.
However, for counterfactuals, a conditional/subjunctive marker such as the Russian бы (by) generally appears in both condition and consequent clauses, and this normally accompanies the past tense form of the verb.