Grammatical mood

In linguistics, grammatical mood is a grammatical feature of verbs, used for signaling modality. In other words, it is the use of verbal inflections that allow speakers to express their attitude toward what they are saying. The term is also used more broadly to describe the syntactic expression of modality – that is, the use of verb phrases that do not involve inflection of the verb itself.
Mood is distinct from grammatical tense or grammatical aspect, although the same word patterns are used for expressing more than one of these meanings at the same time in many languages, including English and most other modern Indo-European languages.
Some examples of moods are indicative, interrogative, imperative, subjunctive, injunctive, optative, and potential. These are all finite forms of the verb. Infinitives, gerunds, and participles, which are non-finite forms of the verb, are not considered to be examples of moods.
Some Uralic Samoyedic languages have more than ten moods; Nenets has as many as sixteen. The original Indo-European inventory of moods consisted of indicative, subjunctive, optative, and imperative. Not every Indo-European language has all of these moods, but the most conservative ones such as Avestan, Ancient Greek, and Vedic Sanskrit have them all. English has indicative, imperative, conditional, and subjunctive moods.
Not all the moods listed below are clearly conceptually distinct. Individual terminology varies from language to language, and the coverage of, for example, the "conditional" mood in one language may largely overlap with that of the "hypothetical" or "potential" mood in another. Even when two different moods exist in the same language, their respective usages may blur, or may be defined by syntactic rather than semantic criteria. For example, the subjunctive and optative moods in Ancient Greek alternate syntactically in many subordinate clauses, depending on the tense of the main verb. The usage of the indicative, subjunctive, and jussive moods in Classical Arabic is almost completely controlled by syntactic context. The only possible alternation in the same context is between indicative and jussive following the negative particle lā.

Realis moods

Realis moods are a category of grammatical moods that indicate that something is actually the case. The most common realis mood is the indicative mood. Some languages have a distinct generic mood for expressing general truths.

Indicative

The indicative mood, or evidential mood, is used for factual statements and positive beliefs. It is the mood of reality. The indicative mood is the most commonly used mood and is found in all languages. Example: "Paul is eating an apple" or "John eats apples".

Irrealis moods

Irrealis moods or non-indicative moods are the set of grammatical moods that indicate that something is not actually the case or a certain situation or action is not known to have happened. They are any verb or sentence mood that is not a realis mood. They may be part of expressions of necessity, possibility, requirement, wish or desire, fear, or as part of counterfactual reasoning, etc.
Irrealis verb forms are used when speaking of an event which has not happened, is not likely to happen, or is otherwise far removed from the real course of events. For example, in the sentence "If you had done your homework, you wouldn't have failed the class", had done is an irrealis verb form.
Some languages have distinct irrealis grammatical verb forms. Many Indo-European languages preserve a subjunctive mood. Some also preserve an optative mood that describes events that are wished for or hoped for but not factual.
Common irrealis moods are the conditional, the subjunctive, the optative, the jussive, and the potential. For other examples, see the main article for each respective mood.

Subjunctive

The subjunctive mood, sometimes called conjunctive mood, has several uses in dependent clauses. Examples include discussing imaginary or hypothetical events and situations, expressing opinions or emotions, or making polite requests. A subjunctive mood exists in English, though it is not an inflectional form of the verb but rather a clause type which uses the bare form of the verb also used in imperatives, infinitives, and other constructions. An example of the English subjunctive is "Jill suggested that Paul take his medicine", as opposed to the indicative sentence "Jill believes that Paul takes his medicine".
Other uses of the subjunctive in English are archaisms, as in "And if he be not able to bring a lamb, then he shall bring for his trespass...". Statements such as "I will ensure that he leave immediately" often sound archaic or formal, and have been largely supplanted by constructions with the indicative, like "I will ensure that he leaves immediately".
Some Germanic languages distinguish between two types of subjunctive moods, for example, the Konjunktiv I and II in German.

Language	Sentence
English	John would eat if he were* hungry.*
Danish	John ville spise, hvis han var sulten.
Dutch	Jan zou eten, als hij honger zou hebben.
French¹	Jean mangerait s’il avait faim.
German	Johannes äße, wenn er hungrig wäre.
Hindi	जॉन खाता अगर उसे भूख होती। jôn khātā agar use bhūkh hotī.
Assamese	জনৰ ভোক লাগিলে খালে হেঁতেন। zônôr bhûk lagile khale hẽten.
Irish	D'íosfadh Seán dá mbeadh* ocras air.*
Italian	Giovanni mangerebbe se avesse fame.
Lithuanian	Jonas valgytų, jei būtų alkanas.
Polish	Jan jadłby, gdyby zgłodniał.
Portuguese	O João comeria se tivesse fome.
Russian	Иван поел бы, если бы был голоден.
Spanish	Juan comería si tuviera hambre.
Swedish	Johan skulle äta, om han vore hungrig.
Slovenian	Janez bi jedel, če bi bil lačen.

¹ In modern usage, the imperfect indicative usually replaces the imperfect subjunctive in this type of sentence.
The subjunctive mood figures prominently in the grammar of the Romance languages, which require this mood for certain types of dependent clauses. This point commonly causes difficulty for English speakers learning these languages.
In certain other languages, the dubitative or the conditional moods may be employed instead of the subjunctive in referring to doubtful or unlikely events.

Conditional

The conditional mood is used for speaking of an event whose realization is dependent upon another condition, particularly, but not exclusively, in conditional sentences. In Modern English, this type of modality is expressed via a periphrastic construction, with the form would + infinitive,, and thus is a mood only in the broad sense and not in the more common narrow sense of the term "mood" requiring morphological changes in the verb. In other languages, verbs have a specific conditional inflection. In German, the conditional mood is identical to one of the two subjunctive moods .
English John would eat if he were hungry.
Basque Jonek jango luke, goserik balu.
Estonian Juhan sööks, kui tal oleks nälg
Finnish Juha söisi, jos hänellä olisi nälkä
French Jean mangerait s'il avait faim.
German Johannes äße, wenn er hungrig wäre.
Also: Johannes würde essen, wenn er hungrig wäre.
Hindi जॉन खाता अगर उसे भूख होती।
jôn khātā agar usē bhūkh hotī.
Irish D'íosfadh Seán dá mbeadh ocras air.
Italian Giovanni mangerebbe se avesse fame.
Lithuanian Jonas valgytų, jei būtų alkanas.
Polish Jan jadłby, gdyby zgłodniał.
Portuguese João comeria se estivesse com fome.
Russian Иван поел бы, если бы был голоден.
Spanish Juan comería si tuviera hambre.
Swedish Johan skulle äta, om han vore hungrig.

In the Romance languages, the conditional form is used primarily in the apodosis of conditional sentences, and in a few set phrases where it expresses courtesy or doubt. The main verb in the protasis is usually in the subjunctive or in the indicative mood. However, this is not a universal trait and among others in German, Finnish, and Romanian, the conditional mood is used in both the apodosis and the protasis. A further example is a sentence "I would buy a house if I earned a lot of money".

Irish has conditional marking in both clauses: d'íosfadh 'would eat, would have eaten' and beadh 'would be, would have been', along with a specific irrealis conditional dá 'if', which contrasts with the realis conditional má 'if'.
In Finnish, both clauses likewise have the conditional marker -isi-: Ostaisin talon, jos ansaitsisin paljon rahaa.
In Polish, the conditional marker -by also appears twice: Kupiłbym dom, gdybym zarabiał dużo pieniędzy.
In Hindi, the conditional markers -ता, -ती, -ते and -तीं comes twice: मैं घर खरीदता अगर बहौत पैसे कमाता।. The conditional form in Hindi corresponds to perfect conditional of Romance and the Germanic languages. So, the sentence literally translate to "I would have bought a house if I earned a lot of money."

Due to English's status as a lingua franca, a common error among second-language speakers is to use "would" in both clauses. For example, *"I would buy if I would earn...". In Dutch, for instance, inserting zouden "would" in the if-clause is not considered grammatically incorrect: ik zou een huis hebben gekocht, als ik veel geld zou verdienen.''

English	John would eat if he were hungry.
Basque	Jonek jango luke, goserik balu.
Estonian	Juhan sööks, kui tal oleks nälg
Finnish	Juha söisi, jos hänellä olisi nälkä
French	Jean mangerait s'il avait faim.
German	Johannes äße, wenn er hungrig wäre. Also: Johannes würde essen, wenn er hungrig wäre.
Hindi	जॉन खाता अगर उसे भूख होती। jôn khātā agar usē bhūkh hotī.
Irish	D'íosfadh Seán dá mbeadh ocras air.
Italian	Giovanni mangerebbe se avesse fame.
Lithuanian	Jonas valgytų, jei būtų alkanas.
Polish	Jan jadłby, gdyby zgłodniał.
Portuguese	João comeria se estivesse com fome.
Russian	Иван поел бы, если бы был голоден.
Spanish	Juan comería si tuviera hambre.
Swedish	Johan skulle äta, om han vore hungrig.