A conditional is understood as expressing its consequent under the temporary hypothetical assumption of its antecedent.
The consequent can precede the "if"-clause and the word "if" itself may be omitted or replaced with a different complementizer.
In English conditional sentences, the antecedent (protasis) is a dependent clause, most commonly introduced by the complementizer if.
It may also be shortened by verb phrase ellipsis; a minimal conditional sentence could therefore be something like "Would you?"
Like other languages, English uses past tense morphology to indicate that the speaker regards the antecedent as impossible or unlikely.
Occasionally, mainly in a formal and somewhat archaic style, a subjunctive is used in the zero-conditional condition clause (as in "If the prisoner be held for more than five days, ...).
In some common fixed expressions or in old-fashioned or formal contexts, the present subjunctive is occasionally found.
), as described under Uses of English verb forms § Dependent clauses.
As noted in the following section, it may be possible to express a statement about a hypothetical future situation using either the first or second conditional pattern, with little specific difference in meaning.
If the condition clause uses the past tense of another verb, it may be replaced by the auxiliary construction were to + infinitive (particularly if it has hypothetical future reference); if this is done, then inversion can be applied here too: Another possible pattern is if it weren't for... (inverted form: were it not for ...), which means something like "in the absence of ...".
When referring to hypothetical future circumstance, there may be little difference in meaning between the first and second conditional (factual vs. counterfactual, realis vs. irrealis).
That used, the above examples can be written as such: The condition clause can undergo inversion, with omission of the conjunction: Another possible pattern (similar to that mentioned under the second conditional) is if it hadn't been for... (inverted form: had it not been for ...), which means something like "in the absence of ...", with past reference.
More commonly, will appears in condition clauses where it has a modal meaning, rather than marking the future.
Relevant meanings include willingness, persistence, or strong disapproval:[4][6][7] In the second and third sentences will is stressed, and cannot be contracted to "'ll".
It is not usually found in more formal writing; however some sources describe it as acceptable US English, no longer labeling it colloquial.
Certain condition clauses (if-clauses) can be cast without any conjunction such as if or unless, instead using subject–auxiliary inversion to indicate their meaning.
The principal constructions are as follows: Inversion is also possible when the present subjunctive be is used (e.g. "Be he called on by God..." for "If he be called on by God..."), but this is archaic usage for condition clauses; it is still occasionally found in dependent clauses expressing "no matter whether ...", e.g. "Be they friend or foe ..." (equivalent to "Whether they be friend or foe ...").