Conditional mood

The conditional mood is a grammatical mood used in conditional sentences to express a proposition whose validity is dependent on some condition, possibly counterfactual.
It may refer to a distinct verb form that expresses the conditional set of circumstances proper in the dependent clause or protasis, or which expresses the hypothetical state of affairs or uncertain event contingent to it in the independent clause or apodosis, or both. Some languages distinguish more than one conditional mood; the East African language Hadza, for example, has a potential conditional expressing possibility, and a veridical conditional expressing certainty. Other languages do not have a conditional mood at all. In some informal contexts, such as language teaching, it may be called the "conditional tense".
Some languages have verb forms called "conditional" although their use is not exclusive to conditional expression. Examples are the English and French conditionals, which are morphologically futures-in-the-past, and of which each has thus been referred to as a "so-called conditional" in modern and contemporary linguistics. The English would construction may also be used for past habitual action.
This article describes the formation of the conditional forms of verbs in certain languages. For fuller details of the construction of conditional sentences, see Conditional sentence.

Germanic languages

English

does not have an inflective conditional mood, except in as much as the modal verbs could, might, should and would may in some contexts be regarded as conditional forms of can, may, shall and will respectively. What is called the English conditional mood is formed periphrastically using the modal verb would in combination with the bare infinitive of the following verb.
English has three types of conditional sentences, which may be described as factual, predictive, and counterfactual. As in many other languages, it is only the counterfactual type that causes the conditional mood to be used.
Conditionality may be expressed in several tense–aspect forms. These are the conditional simple, the conditional progressive, the conditional perfect, and conditional perfect progressive. For the uses of these, see Uses of English verb forms. The conditional simple and conditional progressive may also be called the present conditional, while the perfect forms can be called past conditional.
For details of the formation of conditional clauses and sentences in English, see English conditional sentences.

German

In German, the following verbal constructions are sometimes referred to as conditional :

Subjunctive mood#Konjunktiv II, corresponds to English's present conditional. It is formed either with vowel change or with the auxiliary verb werden in its subjunctive form, plus the infinitive:
Konjunktiv II, Pluperfect#German corresponds to English's past conditional. It is a form of the perfect construction, using a form of the auxiliary haben or sein together with the past participle of the main verb. The auxiliary in this case takes past subjunctive form: hätte/st/t/n or wäre/st/t/n.

For more information, see German conjugation.

Dutch

The main conditional construction in Dutch involves the past tense of the verb zullen, the auxiliary of the future tenses, cognate with English 'shall'.
The latter tense is sometimes replaced by the past perfect.

Romance languages

While Latin did not conjugate separately for the conditional, most of the Romance languages developed a conditional paradigm. The evolution of those forms is a well-known example of grammaticalization whereby a syntactically and semantically-independent word becomes a bound morpheme with a highly-reduced semantic function. The Romance conditional forms are derived from the Latin infinitive, followed by a finite form of the verb. This verb originally meant "to have" in Classical Latin but in Late Latin picked up a grammatical use as a temporal or modal auxiliary. The fixing of word order and the phonological reduction of the inflected forms of habēre eventually led to the fusion of the two elements into a single synthetic form.
In French, Spanish, Portuguese, Catalan and Occitan, the conditional endings come from the imperfect of Latin. For example, in the first person singular:

Language	Example
Late Latin	cantāre habēbam
Vulgar Latin	*cantar-ea
Old Italian	cantarìa
Spanish	cantaría
Portuguese	cantaria
Catalan	cantaria
Occitan	cantariái
French	chanterais
Old French	chantereie, -eve

A trace of the historical presence of two separate verbs can still be seen in the possibility of mesoclisis in conservative varieties of European Portuguese in which an object pronoun may appear between the verb stem and the conditional ending.

Italian

Old Italian had originally three different forms of conditional:

one based on infinitive + conditional endings from the perfect of Latin,, e.g. canterebbe - he would sing ;
one based on infinitive + conditional endings from the imperfect of Latin,, e.g. cantarìa ;
one derived directly from Latin pluperfect, e.g. cantàra.

Only the Tuscan form survives in modern Italian:
The second and third types have slowly disappeared remaining until the 19th century in some poetic composition for metric needs.

Romanian

uses a periphrastic construction for the conditional, e.g. 1sg aș, 2sg ai, 3sg/pl ar, 1pl am, 2pl ați + cânta 'sing'. The modal clitic mixes forms of Latin habēre:

ai, am, and ați are presumably from the Latin imperfect ;
ar allegedly comes from the imperfect subjunctive ; and
aș continues Latin pluperfect subjunctive habessim which formed the basis of the Romance imperfect subjunctive.

Old Romanian, on the other hand, used a periphrastic construction with the imperfect of vrea 'to want' + verb, e.g. vrea cânta 'I would sing', vreai cânta 'you would sing', etc. Until the 17th century, Old Romanian also preserved a synthetic conditional, e.g. cântare 'I would sing', cântarem 'we would sing', and darear 'he would give', retained from either the Latin future perfect or perfect subjunctive. Aromanian and Istro-Romanian have maintained the same synthetic conditional:

Aromanian: s-cãntárimu 'I would sing', s-cãntári, s-cãntári, s-cãntárimu, s-cãntáritu, s-cãntári; and
Istro-Romanian: aflår 'I would find', aflåri, aflåre, aflårno, aflåritu, aflåru.
Portuguese

In Portuguese, the conditional is formed by the imperfect form of habēre affixed to the main verb's infinitive. However, in the spoken language, the periphrastic form is also extremely common.

Grammatical person	falar	comer	rir
Eu	Falaria / Iria falar / Ia falar	Comeria / Iria comer / Ia comer	Riria / Iria rir / Ia rir
Tu	Falarias / Irias falar / Ias falar	Comerias / Irias comer / Ias comer	Ririas / Irias rir / ias rir
Ele/Ela	Falaria / Iria falar / Ia falar	Comeria / Iria comer / Ia comer	Riria / Iria rir / Ia rir
Nós	Falaríamos / Iríamos falar / Íamos falar	Comeríamos / Iríamos comer / Íamos comer	Riríamos / Iríamos rir / Íamos rir
Vós	Falaríeis / Iríeis falar / Íeis falar	Comeríeis / Iríeis comer / Íeis comer	Riríeis / Iríeis rir / Íeis rir
Eles/Elas	Falariam / Iriam falar / Iam falar	Comeriam / Iriam comer / Iam comer	Ririam / Iriam rir / Iam rir

The Portuguese conditional is also called past future futuro do pretérito, as it describes both conjectures that would occur given a certain condition and actions that were to take place in the future, from a past perspective. When the conditional has the former purpose, it imperatively comes along with a conditional subordinate clause in the past subjunctive.
The conditional is also one of the two Portuguese tenses that demand mesoclisis when proclisis is forbidden since enclisis is always considered ungrammatical.

Não o falaríamos/ Não te falaríamos Grammatical use of proclisis.
Falá-lo-íamos/ Falar-te-íamos Grammatical use of mesoclisis.
O falaríamos/ Te falaríamos Ungrammatical use of proclisis.
Falaríamo-lo/ Falaríamo-te Ungrammatical use of enclisis.
Spanish

In Spanish, the conditional is formed by the infinitive of the verb with a postfix for all verbs. For irregular verbs, the stem is modified.

Grammatical person	comprar	vender	dormir	tener	Meaning
yo	compraría	vendería	dormiría	tendría	I would...
tu	comprarías	venderías	dormirías	tendrías	you would...
él/ella/usted	compraría	vendería	dormiría	tendría	he/she/you would...
nosotros	compraríamos	venderíamos	dormiríamos	tendríamos	we would...
vosotros	compraríais	venderíais	dormiríais	tendríais	you would...
ellos/ellas/ustedes	comprarían	venderían	dormirían	tendrían	they would...

Slavic languages

Russian

In Russian, the conditional mood is formed by the past tense of the verb with the particle, which usually follows the verb. For example:

This form is sometimes also called the subjunctive mood. For more information on its usage, see Russian verbs.