Conditional sentences are sentences expressing factual implications, or hypothetical situations
and their consequences.
They are so called because the validity of the main clause of the sentence is conditional
on the existence of certain circumstances, which may be expressed in a dependent clause
or may be understood from the context.
A full conditional sentence therefore contains two clauses: the dependent clause expressing
the condition, called the protasis; and the main clause expressing the consequence, called
the apodosis.
An example of such a sentence is the following:
If it rains, the picnic will be cancelled.
Here the condition is expressed by the clause "If it rains", this being the protasis, while
the consequence is expressed by "the picnic will be cancelled", this being the apodosis.
In terms of logic, the protasis corresponds to the antecedent, and the apodosis to the
consequent.
Languages use a variety of grammatical forms and constructions in conditional sentences.
The forms of verbs used in the protasis and apodosis are often subject to particular rules
as regards their tense and mood.
Many languages have a specialized type of verb form called the conditional mood – broadly
equivalent in meaning to the English "would" – for use in some types of conditional sentence.
Types of conditional sentence There are various ways of classifying conditional
sentences.
One distinction is between those that state an implication between facts, and those that
set up and refer to a hypothetical situation.
There is also the distinction between conditionals that are considered factual or predictive,
and those that are considered counterfactual or speculative.
Implicative and predictive A conditional sentence expressing an implication
essentially states that if one fact holds, then so does another.
The facts are usually stated in whatever grammatical tense is appropriate to them; there are not
normally special tense or mood patterns for this type of conditional sentence.
Such sentences may be used to express a certainty, a universal statement, a law of science, etc.:
If you heat water to 100 degrees, it boils.
If the sea is stormy, the waves are high.
They can also be used for logical deductions about particular circumstances:
If it's raining here now, then it was raining on the West Coast this morning.
If it's raining now, then your laundry is getting wet.
If it's raining now, there will be mushrooms to be picked next week.
If he locked the door, then Kitty is trapped inside.
A predictive conditional sentence concerns a situation dependent on a hypothetical future
event.
The consequence is normally also a statement about the future, although it may also be
a consequent statement about present or past time.
If I become President, I'll lower taxes.
If it rains this afternoon, everybody will stay home.
If it rains this afternoon, then yesterday's weather forecast was wrong.
If it rains this afternoon, your garden party is doomed.
What will you do if he invites you?
If you see them, shoot!
Counterfactual
In a counterfactual or speculative conditional sentence, a situation is described as dependent
on a condition that is known to be false, or presented as unlikely.
The time frame of the hypothetical situation may be past, present or future, and the time
frame of the condition does not always correspond to that of the consequence.
For example:
If I were king, I could have you thrown in the dungeon.
If I won the lottery, I would buy a car.
If he said that to me, I would run away.
If you had called me, I would have come.
If you had done your job properly, we wouldn't be in this mess now.
The difference in meaning between a "counterfactual" conditional with a future time frame, and
a "predictive" conditional as described in the previous section, may be slight.
For example, there is no great practical difference in meaning between "If it rained tomorrow,
I would cancel the match" and "If it rains tomorrow, I will cancel the match".
It is in the counterfactual type of conditional sentence that the grammatical form called
the conditional mood is most often found.
For the uses of particular verb forms and grammatical structures in the various types
and parts of conditional sentences in certain languages, see the following sections.
Grammar of conditional sentences Languages have different rules concerning
the grammatical structure of conditional sentences.
These may concern the syntactic structure of the condition clause and consequence, as
well as the forms of verbs used in them.
Rules for English and certain other languages are described below; more information can
be found in the articles on the grammars of individual languages.
English
In English conditional sentences, the condition clause is most commonly introduced by the
conjunction if, or sometimes other conjunctions or expressions such as unless, provided, providing
and as long as.
Certain condition clauses can also be formulated using inversion without any conjunction.
In English language teaching, conditional sentences are often classified under the headings
zero conditional, first conditional, second conditional, third conditional and mixed conditional,
according to the grammatical pattern followed.
A range of variations on these structures are possible.
Zero conditional "Zero conditional" refers to conditional sentences
that express a simple implication, particularly when both clauses are in the present tense:
If you don't eat for a long time, you become hungry.
This form of the conditional expresses the idea that a universally known fact is being
described:
If you touch a flame, you burn yourself.
The act of burning oneself only happens on the condition of the first clause being completed.
However such sentences can be formulated with a variety of tenses, as appropriate to the
situation.
First conditional "First conditional" refers to predictive conditional
sentences; here, normally, the condition is expressed using the present tense and the
consequence using the future:
If you make a mistake, someone will let you know.
Second conditional "Second conditional" refers to the pattern
where the condition clause is in the past tense, and the consequence in conditional
mood.
This is used for hypothetical, counterfactual situations in a present or future time frame.
If I liked parties, I would attend more of them.
If it were to rain tomorrow, I would dance in the street.
The past tense used in the condition clause is historically the past subjunctive; however
in modern English this is identical to the past indicative except in certain dialects
in the case of the verb be, where the indicative is was and the subjunctive were.
In this case either form may be used:
If I was/were rich, there would be plenty of money available for this project.
Third conditional "Third conditional" is the pattern where the
condition clause is in the past perfect, and the consequence is expressed using the conditional
perfect.
This is used to refer to hypothetical, counterfactual situations in the past
If you had called me, I would have come.
Mixed conditionals "Mixed conditional" usually refers to a mixture
of the second and third conditionals.
Here either the condition or the consequence, but not both, has a past time reference:
If you had done your job properly, we wouldn't be in this mess now.
If we were soldiers, we wouldn't have done it like that.
Latin Conditional sentences in Latin are traditionally
classified into three categories, based on grammatical structure.
simple conditions present tense [if present indicative then
indicative] past tense [if perfect/imperfect indicative
then indicative]
future conditions "future more vivid" [if future indicative
then future indicative] "future less vivid" [if present subjunctive
then present subjunctive]
contrafactual conditions "present contrary-to-fact" [if imperfect subjunctive
then imperfect subjunctive] "past contrary-to-fact" [if pluperfect subjunctive
then pluperfect subjunctive]
French In French, the conjunction corresponding to
"if" is si.
The use of tenses is quite similar to English: In implicative conditional sentences, the
present tense is used in both clauses.
In predictive conditional sentences, the future tense or imperative generally appears in the
main clause, but the condition clause is formed with the present tense.
This contrasts with dependent clauses introduced by certain other conjunctions, such as quand,
where French uses the future.
In counterfactual conditional sentences, the imperfect is used to express the condition.
The main clause contains the conditional mood.
In counterfactual conditional sentences with a past time frame, the condition is expressed
using the pluperfect e.g., and the consequence with the conditional perfect.
Again these verb forms parallel those used in English.
As in English, certain mixtures and variations of these patterns are possible.
See also French verbs.
Italian Italian uses the following patterns:
Present tense in both parts of an implicative conditional.
Future tense in both parts of a predictive conditional sentence.
In a counterfactual conditional, the imperfect subjunctive is used for the condition, and
the conditional mood for the main clause.
A more informal equivalent is to use the imperfect indicative in both parts.
In a counterfactual conditional with past time frame, the pluperfect subjunctive is
used for the condition, and the past conditional for the main clause.
See also Italian verbs.
Slavic languages In Slavic languages, such as Russian, clauses
in conditional sentences generally appear in their natural tense 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.
See Russian grammar, Bulgarian grammar, etc. for more detail.
Logic While the material conditional operator used
in logic is sometimes read aloud in the form of a conditional sentence, the intuitive interpretation
of conditional statements in natural language does not always correspond to the definition
of this mathematical relation.
Modelling the meaning of real conditional statements requires the definition of an indicative
conditional, and contrary-to-fact statements require a counterfactual conditional operator,
formalized in modal logic.
See also Anankastic conditional
English modal auxiliary verb Conditional mood
Subjunctive mood References
External links Conditional Sentences for advanced learners
Using conditional clauses in English with clear examples
English conditional clauses explanations with examples
Latin Conditionals French Conditionals