It may refer to a distinct verb form that expresses the conditional set of circumstances proper in the dependent clause or protasis (e.g. in Turkish or Azerbaijani[a]), or which expresses the hypothetical state of affairs or uncertain event contingent to it in the independent clause or apodosis, or both (e.g. in Hungarian or Finnish[b]). 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[which?] 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 or French conditionals (an analytic construction in English,[c] but inflected verb forms in French), which are morphologically futures-in-the-past, and of which each has thus been referred to as a "so-called conditional" (French: soi-disant conditionnel) in modern and contemporary linguistics (e.g. French je chanterais, from Late Latin cant?re hab?bam, in si vous me le permettiez, je chanterais, "if you allowed me to do so, I would sing" [so-called conditional] vs. j'ai dit que je chanterais, "I said that I would sing" [future-in-the-past]). The English would construction may also be used for past habitual action ("When I was young I would happily walk three miles to school every day").
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 (and for English specifically, English conditional sentences).
English does not have[d] an inflective (morphological) 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 (or just the conditional) is formed periphrastically using the modal verb would in combination with the bare infinitive of the following verb. (Occasionally should is used in place of would with a first person subject - see shall and will. Also the aforementioned modal verbs could, might and should may replace would in order to express appropriate modality in addition to conditionality.)
English has three types of conditional sentences, which may be described as factual ("conditional 0": "When I feel well, I sing"), predictive ("conditional I": "If I feel well, I will sing"), and counterfactual ("conditional II" or "conditional III": "If I felt well, I would sing"; "If I had felt well, I would have sung"; or "Were I well (if I were well) I would have sung"). 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 simple conditional (would sing), the conditional progressive (would be singing), the conditional perfect (would have sung), and conditional perfect progressive (would have been singing). For the uses of these, see Uses of English verb forms. The conditional simple and 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.
In German, the following verbal constructions are sometimes referred to as conditional (German: Konditional):
For more information, see German conjugation.
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 (plusquamperfect).
While Latin used the indicative and subjunctive in conditional sentences, most of the Romance languages developed a conditional paradigm. The evolution of these forms (and of the innovative Romance future tense 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 (and future) forms are derived from the Latin infinitive followed by a finite form of the verb hab?re. 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 (infinitive + auxiliary) and the phonological reduction of the inflected forms of hab?re eventually led to the fusion of the two elements into a single synthetic form.
|Late Latin||cant?re hab?bam|
|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, where an object pronoun can appear between the verb stem and the conditional ending (e.g. cantá-lo-ia; see Portuguese personal pronouns § Proclisis, enclisis, and mesoclisis).
Only the tuscan form survives in modern Italian:
The second and third types have slowly disappeared remaining until XIX century in some poetic composition for metric needs. 
Romanian uses a periphrastic construction for the conditional, e.g. 1sg a?, 2sg ai, 3sg/pl ar, 1pl am, 2pl a?i + cânta 'sing'. The modal clitic mixes forms of Latin hab?re:
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 (or a mixture of both).Aromanian and Istro-Romanian have maintained the same synthetic conditional:
In Portuguese, the conditional is formed by the imperfect form of hab?re affixed to the main verb's infinitive. However, in spoken language, the periphrastic form is also extremely common.
|Grammatical person||falar (to speak)||comer (to eat)||rir (to laugh)|
|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|
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 which demand mesoclisis when proclisis is forbidden - since enclisis is always considered ungrammatical.
|Grammatical person||comprar (to buy)||vender (to sell)||dormir (to sleep)||tener (to have)||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 ...|
Polish forms the conditional mood in a similar way to Russian, using the particle by together with the past tense of the verb. This is an enclitic particle, which often attaches to the first stressed word in the clause, rather than following the verb. It also takes the personal endings (in the first and second persons) which usually attach to the past tense. For example:
The clitic can move after conjunctions, e.g.:
There is also a past conditional, which also includes the past tense of the copular verb by?, as in by?(a)bym ?piewa?(a) ("I would have sung"), but this is rarely used.
For details see Polish verbs.
Hungarian uses a marker for expressing the conditional mood. This marker has four forms: -na, -ne, -ná and -né. In the present tense, the marker appears right after the verb stem and just before the affix of the verbal person. For example: I would sit: ül (sit) + ne + k (referring to the person I) = ülnék. (In Hungarian, when a word ends with a vowel, and a suffix or a marker or an affix is added to its end, the vowel becomes long.) When making an if-sentence, the conditional mood is used in both apodosis and the protasis:
In Hungarian, the past tense is expressed with a marker as well, but two verbal markers are never used in sequence. Therefore, the auxiliary verb volna is used for expressing the conditional mood in the past. The word volna is the conditional form of the verb van (be). The marker of past is -t/-tt, and is put exactly the same place as the marker of conditional mood in the present.
Expressing a future action with the conditional mood is exactly the same as the present, although an additional word referring to either a definite or indefinite time in the future is often used: majd (then), holnap (tomorrow), etc.
The conditional mood is often used with potential suffixes attached to the verb stem (-hat/-het), and the two are therefore often confused.
In Finnish the conditional mood is used in both the apodosis and the protasis, just like in Hungarian. It uses the conditional marker -isi-: