Latin conditional clauses

Conditional clauses in Latin are clauses which start with the conjunction sī 'if' or the equivalent. The 'if'-clause in a conditional sentence is known as the protasis, and the consequence is called the apodosis.
Conditional clauses are generally divided into three types: open conditions, when the truth of the condition is unknown ; ideal conditions, in which the speaker imagines a situation or event which might occur in the future ; and unreal conditions, referring to an event or situation in the present or past known to be contrary to fact. These three are also sometimes referred to as Type 1, Type 2, and Type 3 respectively. Open conditional clauses in turn can be divided into particular and general.
Open conditional sentences generally use the indicative mood in both protasis and apodosis, although in some general conditions the subjunctive mood is used in the protasis. Ideal and unreal conditionals use the subjunctive in the protasis, and usually they also use the subjunctive in the apodosis, though sometimes the indicative may be used. Conditional clauses of comparison also use the subjunctive mood in the protasis.
Conditional clauses sometimes overlap in meaning with other types of clause, such as concessive, causal, or temporal.
The conjunction sī is only rarely used in classical Latin to introduce indirect questions, although this usage is found in medieval Latin and is common in Greek and in modern Romance languages such as French and Italian. The use of 'if' to make a wish, found in ancient Greek, is not usual in Latin, except sometimes in poetry.

Main types of conditional clause

A summary of the main types of conditional clause is given in the table below. The subjunctive is used in the protasis of ideal and unreal conditions, and also in some types of general conditions. In the apodosis of ideal and unreal conditions, the verb is usually subjunctive, but sometimes the indicative is used.
A difference from English grammar is that in open future conditions, it is usual in Latin to use one of the future tenses, when English has the present tense.
Apart from the types mentioned below it is also possible to have mixed conditionals, for example with different tenses in protasis and apodosis.

Conditional conjunctions

Positive conjunctions

The usual conjunction in a conditional clause is sī, for which see the examples below.

The conjunction sīn 'but if', 'if on the other hand' is used for the second of two opposite conditions:

The pair sīve... sīve 'whether... or' often does not introduce a full conditional clause and an appropriate verb has to be supplied by the reader:
Sometimes, however, a verb is added:
Sometimes the two words can introduce two alternative apodoses, in the same way as sī... sīn:

The combination quod sī 'but if' or 'if, however' can also introduce an alternative:

The combination etsī means 'although', and it is often followed in the apodosis by tamen 'nonetheless':
Another frequent combination, slightly more emphatic, is etiam sī 'even if', 'even though':

The conjunction siquidem or sī quidem means 'if indeed' or 'if it's true that':
It also can have a causal meaning, 'in view of the fact that':

Another combination, sī modō 'if indeed', expresses doubt that the situation mentioned is in fact true:
In other sentences it has the meaning similar to dummodo 'provided that':

Indefinite conditional clauses often use the combinations sī quis 'if anyone', sī quid 'if anything', sī quī 'if any', sī quisquam 'if anyone at all', sī quicquam 'if anything at all', sī quandō 'if at any time', 'if ever', sī quā 'if in any way':
However, it is also possible to use alternative words such as sī aliquis 'if someone', sī unquam 'if ever', and sī ūllus 'if any', which tend to be more emphatic:

Negative conditions

When the conditional clause is negative, there are various possibilities: nisi 'if not', 'unless', sī... nōn 'if not', nī 'were it not that' and sī minus 'otherwise'.

nisi means 'unless' or 'if not' or 'except':
Sometimes nisi and sī are combined:
The above kind of nisi-clause, called 'exceptive nisi', leaves open the possibility that the condition is not met; each of the above examples could be translated 'unless perhaps' or 'unless by chance'. There is another usage of nisi, called 'exclusive nisi', which combined with a negative apodosis gives the logical sense of 'only if':

The combination of sī and nōn is also commonly used:
The combination sī nōn is preferred when a particular word is made negative:

The conjunction nī is less commonly used, except in Livy and the poets. It is not used by Caesar, and only occasionally in Cicero. In the classical writers it is most often used in unreal conditions:
Less often nī is used in open conditions:

Another way of expressing the negative is with sī minus:
sī minus rather than sī nōn is also used if the verb has to be supplied from the context:

Open conditions

Present or past

A present open conditional normally has the indicative in both halves. Various tenses are possible, but the present or perfect are common:
The following combines an imperfect tense in the protasis and future in the apodosis:
A conditional clause is often found after quid mīrum 'what is surprising?'
Usually the verb of the apodosis is also indicative, but other moods are possible, such as the imperative below:

Future

In a future conditional, the protasis usually has one of the future tenses, where English has the simple present. In the following, the simple future tense is used:
Often, however, a future conditional uses the future perfect indicative, to refer to an event that must take place first before the consequence happens:
Sometimes both halves of the conditional can have the future perfect tense, though this is rare:
If the apodosis of a future conditional is a command, the future imperative is used, rather than the present imperative:
The use of the present subjunctive sī possim 'if perhaps I can' in the following example adds uncertainty:
Although the future tense is usual in a protasis referring to the future, sometimes, as in English, in colloquial Latin a present tense is used:

General or iterative conditions

With the indicative

With general or iterative conditions, in writers of the classical period, it was usual to use the indicative mood, as in the following examples:
Sometimes, just as with iterative temporal clauses, a perfect indicative in the protasis is followed by a present indicative in the main clause:
In a past context, this becomes sī with the pluperfect indicative:

With the subjunctive

In later writers a protasis with iterative meaning could sometimes use the subjunctive mood:

2nd person singular generalisation

When a generalisation uses the 2nd person singular in a condition, meaning 'one' or 'anyone', the verb is usually in the subjunctive mood even in classical writers:
The following similarly uses the perfect subjunctive with the 2nd person:
The subjunctive is also used in the apodosis of a generalisation if it has a 2nd person singular verb:

Ideal conditions

Ideal conditions (future)

Ideal conditions are those in which the speaker supposes a situation or an event which might occur in future, at least in the imagination. There is generally an assumption on the speaker's part that the event is not going to take place.

Subjunctive in the apodosis

The tense of an ideal condition is usually present subjunctive, while the main clause usually has the present subjunctive also:
The following uses the perfect subjunctive in the protasis:
In the following example, the perfect subjunctive in the main clause is used to describe a future potential result:
The following has the perfect subjunctive in both clauses:

Indicative in the apodosis

Sometimes, however, the indicative is used in the main clause, as in the following:
Another phrase using the indicative with potential meaning is longum est, which means 'it would take a long time' or 'it would be tedious'. It is frequently used by Cicero as well as other writers:

Past ideal conditionals

An ideal condition can occur in a past context also, in which case it uses the imperfect subjunctive. In the following, the apodosis has the imperfect subjunctive:
In the following, the verb in the apodosis is imperfect indicative:
Although conditionals of this kind use sī with the imperfect subjunctive in the same way as an unreal conditional, the meaning is different. In an unreal conditional, the imperfect subjunctive refers to a situation contrary to fact at the present time or at the time of the story, while in a past ideal conditional, the imperfect subjunctive refers prospectively to a situation that might have occurred at a later time than the time of the narrative.

Unreal conditions

Present unreal

In an unreal or counterfactual conditional sentence the imperfect subjunctive describes a situation contrary to fact in the present and what would follow if that situation were true. The apodosis also usually has the same tense:
Woodcock notes that in early Latin such as Plautus, the present subjunctive rather than the imperfect is often used to represent a present-time counterfactual condition:
In early Latin there is thus a blurring of the distinction between the ideal and the unreal conditional.

Past unreal

The pluperfect subjunctive, ending in -ssem, represents an event contrary to fact in the past. The same tense is usually used both in the protasis and the apodosis:
When the verb in apodosis is passive, in some authors the imperfect subjunctive esset can be replaced by foret to give a potential meaning to the pluperfect subjunctive:
In other authors, however, the same meaning is expressed using a perfect participle + esset:
Sometimes a pluperfect subjunctive is followed by an imperfect or vice versa:
Sometimes an imperfect subjunctive refers to the past rather than the present, and represents a hypothetical situation prevailing at the time of the event described in the apodosis:
Sometimes in poetry, an unreal conditional uses the present or perfect subjunctive as if it were an ideal conditional:
An imperfect subjunctive can sometimes be used in poetry with a similar meaning:

Indicative in the apodosis

Although most unreal conditionals have the subjunctive in the apodosis, it is also possible, just as with ideal conditions, sometimes to use the indicative, especially if the verb is one of possibility or obligation:
The imperfect indicative is used for actions that were interrupted. The protasis is usually negative:
The perfect indicative with paene 'almost' indicates an event that nearly took place:
The pluperfect indicative is sometimes used for events that looked almost certain to happen:
In later, post-classical Latin, it became regular for the indicative to be used in the apodosis of an unreal conditional, as in this example from Gregory of Tours :

Conditional clauses of comparison

Expressions such as tamquam sī 'as if', aequē ac sī 'equally as if', perinde ac sī, proinde ac sī, pariter ac sī 'in the same way as if', velut sī, tamquam 'as though' introduce conditional clauses of comparison. As with ideal and unreal conditions, the verb in the conditional clause is usually in the subjunctive mood. However, the tenses differ from ordinary ideal and unreal conditionals. The main verb is usually either indicative or imperative, and the subordinate clause follows the tense of this according to the sequence of tenses rule. Thus the present subjunctive is usual if the main verb is in the present tense:
The perfect subjunctive can be used to refer to an imaginary past situation in a primary-context sentence:
The following example is exceptional in that the imperfect subjunctive is used in the 'as if' clause, even though the main verb is primary:
When the main verb is perfect or pluperfect, the verb in the conditional clause is imperfect subjunctive, if it imagines a situation coinciding in time with the main verb:
The pluperfect subjunctive is used for an imagined event preceding the time of main verb in a historic context:

'If by chance' or 'in case'

A common idiom in Latin is for a conditional clause, especially one starting sī forte 'if by chance', to mean 'to see if by chance' or 'on the off chance that'. This is common in contexts such as 'go to see if', 'try to see if' and 'wait to see if':
In the following example, the present indicative is used:
However, in most such sentences, since there is some idea of purpose, the subjunctive mood is used. The following uses the present subjunctive, since it follows a present tense verb:
The following use the imperfect subjunctive, since the context is historic:
The word sī in conditionals of this kind can also be translated 'in case':
In the following epistolary tenses are used, so that the subjunctive is pluperfect rather than perfect:

Wishes

The use of sī in wishes is rare in Latin, since the usual particle introducing a wish is utinam. However, occasionally in poetry a wish may be expressed with ō sī... followed by a subjunctive mood verb. The construction is described by Gildersleeve & Lodge as 'poetical and very rare':

Conditionals in indirect speech

Indirect present and future conditions

Subordinate clauses in indirect speech usually use the subjunctive mood. However, if the introductory verb is 1st or 2nd person, the indicative is sometimes retained in a conditional clause, as in the following example:
Otherwise the verb in the protasis becomes subjunctive, as in the following:
The verbs in the above sentences are present subjunctive, despite the historic context, by a process called repraesentātiō, which makes the situation more vivid.
If the verb in an apodosis is a future perfect tense in direct speech, it cannot be expressed using an active verb, but it is possible to use or deponent or passive perfect participle with fore:
When the context is past, a future perfect tense in the protasis usually becomes a pluperfect subjunctive:
However, again by repraesentātiō, the perfect subjunctive is used in the protasis below even in a past context, as if it followed a present tense verb:
In the following sentence, instead of a pluperfect subjunctive, the imperfect subjunctive restituerētur is used with a prospective or future meaning:
The subjunctive foret, can sometimes be used in the protasis instead of esset to refer to a future situation in indirect speech :
Combined with a perfect or deponent participle, foret can stand in a protasis for a future perfect tense of direct speech:

Indirect ideal conditions

Since in indirect speech the subjunctive is usually used in a subordinate clause, the distinction between the ideal conditional and the simple future conditional disappears. In the following examples, only the context indicates that the conditional is ideal:
The perfect subjunctive can also be used if the context is present:
As mentioned above, the perfect participle with fore represents a future perfect passive in the main clause:

Indirect unreal conditions (present)

If a conditional clause in indirect speech describes a present situation contrary to fact, the verb in the apodosis is the periphrastic perfect infinitive, consisting of a future participle + fuisse. The imperfect subjunctive in the protasis remains unchanged, even after a primary tense verb:
In the following, a present unreal situation follows from an unreal past condition:
If the apodosis is an indirect question, the future participle is combined with the perfect subjunctive fuerit instead of the perfect infinitive fuisse:

Indirect unreal conditions (past)

In an indirect past unreal conditional, the apodosis is also often expressed using the future participle plus fuisse, exactly as a present unreal conditional:
When the indirect speech is an indirect question, or a quīn clause, rather than an indirect statement, the construction in the apodosis is the same, except that the perfect infinitive fuisse is replaced by the perfect subjunctive fuerit:
When the verb is passive, futūrum fuisse ut can occasionally be used. However, this is very rare, and only two instances have been noted:
Another way of expressing a passive verb in the apodosis of an unreal conditional in indirect speech is to use the perfect infinitive of possum combined with a present passive infinitive; that is, to write 'could have been done' instead of 'would have been done', since the two are close in meaning:
Similarly in an indirect question, the perfect subjunctive potuerit with the present infinitive can be used:
Another possibility, when the main verb in a quīn-clause is passive, is for the tense to be unchanged from direct speech. Thus in the following, the pluperfect subjunctive is retained:
Even after a historic introductory verb, the perfect subjunctive is usually still retained in a quīn clause :
Exactly the same sequence of tenses is used if the conditional sentence is part of a consecutive clause instead of a quī-clause:
Similarly the perfect subjunctive potuerit, not the pluperfect potuisset, is also usually used even after an historic-tense introductory verb to express a passive verb:
Occasionally, however, after a historic verb the pluperfect subjunctive fuisset is used, but this is rare, and found only in Livy:
The following example is unusual in that it envisages a future event that might one day have taken place if a past situation had been different. The tense used in the apodosis is the imperfect subjunctive:

Indirect questions with

In classical Latin, indirect questions are almost never introduced by sī. Instead, after the verb quaerō 'I ask', the simple suffix -ne is usually used:
However, Livy sometimes uses sī:
According to Lewis and Short's dictionary, this usage derives from the meaning 'to see if by chance' described above. A sentence where this meaning after quaerō is more evident is the following:
Another place where 'if' is used in modern languages is in expressions such as 'I don't know if...'. However, in classical Latin after nesciō or haud sciō 'I do not know', it is usual to use the particle an:
The use of sī in such sentences is very rare, although the following is cited:
The use of sī in both types of sentence is recorded in medieval Latin, however.

Conditional clause equivalents

Occasionally conditional clauses can be made without a conjunction. An imperative is sometimes used:
Sometimes ac 'and' is added, or et:
Sometimes the word sī 'if' or etiamsī 'even if' is simply omitted, usually with a subjunctive verb:
Another possibility is a participle phrase:
In other sentences a conditional is implied in an adjectival phrase: