The Common language has two grammatical moods on verbs, the realis and the irrealis. They correspond broadly to the indicative and subjunctive moods in European languages. Proper, idiomatic use of the realis and irrealis is one of the toughest aspects of Common for language learners. In this topic, we will talk a bit about what they're used for and the rules that determine when you need to use one or the other.

Background and Terminology

First of all, it's necessary to get some terminology out of the way. Realis and irrealis are broad categories of verbal moods, the former pertaining to statements about things that are concrete and real, and the latter pertaining to statements which are hypothetical, counterfactual, etc., essentially anything that is not describing physical reality. The indicative and subjunctive we are used to in European languages are realis and irrealis moods, respectively.

In linguistics there are also specific moods which are confusingly also called the realis and the irrealis  that correspond directly to the indicative and subjunctive. The difference is that realis/irrealis tend to be marked agglutinatively with specific affixes, whereas indicative and subjunctive are marked with fusional verb forms that indicate more than just mood.

By that measure, what Common really has is an indicative and a subjunctive, because the forms of the auxiliaries are definitely fusional. The reason why they're called realis and irrealis is because in Old Common, mood was intended to be marked with an affix, -∅ for the realis and -cir (-/t͡ʃir/ or -/d͡ʒir/) for the irrealis. However, in the late early period, the concrete and abstract gender agreement on verbal auxiliaries was lost and the concrete and abstract forms became conflated with the realis and irrealis. The -cir suffix was lost. This change resulted in a system which was fully fusional for mood and therefore the better terminology would be indicative and subjunctive. However, realis and irrealis are the terms that are still used.

Common-Language Terminology

The relevant technical terminology in the Common language to describe its verbal moods are as follows:

We will continue throughout this article using the accepted English-language terminology, but this will allow you to recognise the Common-language terminology should you encounter it.

Basic Usage

From the point of view of understanding the Common realis/irrealis distinction, it is broadly similar to how the indicative/subjunctive distinction works in continental European languages. If you are familiar with how any of these languages work, it may help you somewhat with Common, although Common has idiosyncracies that have to be learnt, so don't analogise too much. While English has a subjunctive, it is not very distinctive from the indicative or very consistently used, so English is not a good guide.

In Common, it is not possible to use a verb without stating it clearly as realis or irrealis, because in the modern language, the inflection is bound up inseparably in the form of the auxiliary. Native speakers are very attentive and scrupulous about choosing the correct form. In High Common especially, neither form shows any sign of displacing the other. While the realis is certainly much more common, the irrealis sees significant use.

Essentially, you use the realis for statements of fact, either positive or negative, and the irrealis for anything contrary to fact, either positive or negative.

The irrealis might be used for a hypothetical or conditional statement, or for something you wish or choose to be true. It is also used in certain kinds of general statements, and creates both a sense of futurity in some contexts as well as making a more tentative statement about the future. It also has the function of making requests more polite by framing them as hypothetical and contingent on the addressee's agency.

It is generally easiest to think of the realis as the default, as it is more used, and to focus on where you may or must use the irrealis.

Required Use of the Irrealis

The irrealis mood is required in the following situations:

• In any clause governed by the conjunction 'xut', 'if', i.e., the protasis of a conditional statement. Any verb in this clause must be in the irrealis,
• In any dependent clause serving as the object of a verb of desire like 'jusal'. In Common, these are generally noxaj verbs and the object is grammatically treated as an indirect object.
• In if-then statements expressing a conditional sentence, the apodosis, or main clause expressing the consequence, also requires the irrealis if it comes before the protasis governed by 'xut'. If it comes after, the use of the irrealis is optional.
• For conditional statements with a 'hidden if', where the protasis is not stated but the statement is conditional and contingent on some condition.

Examples:

We si an citit xut a hyp zisse ije si ije nox trop.
I would be happy if he/she would tell me that they love me.

In this sentence, the apodosis requires the irrealis because it comes before the protasis. In the protasis, the main verb requires the irrealis, but the nested dependent clause 'si ije nox trop', 'that they love me' uses the realis.

We nox jusal ixi ja mamma y jymjym ije hyp.
I want mama to give me a treat,

The sentence is more literally 'I want that mama a treat to me would give'. The verb in the dependent clause has to be in the irrealis because it is in a dependent clause that is an object, in this case an indirect object, of a verb of desire.

We nux stok ejók zun ija Xarlottawn.
I would go to Charlottetown with you.

This is a 'hidden if' conditional, it expresses a hypothetical without stating a condition, which may come from a conversational antecedent.

Optional Use of the Irrealis

There are a number of other places where the irrealis may not always be mandated by the grammatical environment, but where it may be required for polite communication, expected for idiomatic Common, or help to express a certain shade of meaning,

In general, the irrealis has a hedging quality that reduces certainty in the statement, tends to imply future time, and tends to make requests more polite. Because of this quality, it should conversely be avoided for direct speech.

Yes/No Questions

This category almost should go under required use of the irrealis. When asking a yes/no question, the subject of inquiry is inherently uncertain and the irrealis should be used. The exception is that in some kind of rhetorical question that are closer to being simple statements, or conversely to imply that you expect the answer to be 'yes' but you're asking just to confirm (i.e., in some kinds of polite speech), you could use the realis. Example:

¿Tiu slek ja pikki a skitrem?
Was the cat eating the mouse?

This form uses the irrealis because the speaker doesn't know or assume the answer. But compare to the form:

¿Tene wero ju sy a riske?
Did you do the assignment?

The realis is used here because the speaker is politely assuming the answer must be yes and that therefore the condition described is not hypothetical. Here the realis is actually the polite form, setting the exception that proves the rule.

"Nested" Dependent Clauses

Refer again to the following example:

We si an citit xut a hyp zisse ije si ije nox trop.
I would be happy if he/she would tell me that they love me.

This time, the irrealis verbs are still in bold, but the one realis verb is underlined. Grammatically, the main verb in the apodosis ('we si an citit') has to be in the irrealis because it is an apodosis that appears before its protasis, and 'hyp zisse' has to be in the irrealis because it is the main verb of the protasis. The embedded dependent clause 'si ije nox trop' is not required to be in the irrealis by the grammar of Common, however, and is frequently in the realis in this type of scenario. The proposition is considered to be real in the hypothetical reality set up by the main verb.

However, optionally, the irrealis may bleed into the the nested clauses as well. You could say:

We si an citit xut a hyp zisse ije si ije nux trop.
I would be happy if he/she would tell me that they would love me.

This would mean essentially the same thing as the former statement. What is does is further stress the hypothetical nature of the overall protasis statement, or clarify it if the speaker thinks the listener might not have fully understood. If the speaker fears the listener may be offended by the hypothetical statement, they might use the irrealis at every opportunity including those where it is not strictly required to distance themselves from any perception of endorsing the propostion.

This is also an area where dialectal variation is seen - use of the irrealis in the nested dependent clauses is more common in some dialects than others.

Conditionals with Following ('Hanja') Apodosis

The main clause of a conditional statement which comes after the dependent 'xut' protasis may use the realis, especially if it is introduced with 'hanja', 'and then'. The realis would be used to express an inevitability. However, if you want to hedge the consequence and make it seem less certain, you can still use the irrealis in the apodosis.

Xut ja pikki ti slek a skitrem, hanja a sy se an citit.
If the cat eats the mouse, the person will be happy.

In this example, the realis is used in the apodosis, where the irrealis would be required if it were placed before the protasis, and it expresses certainty in the outcome. Optionally you could say:

Xut ja pikki ti slek a skitrem, hanja a sy si an citit.
If the cat eats the mouse, the person would be happy.

This is also grammatical and hedges the certainty in the inevitability of the predicted outcome.

Hypothetical General Statements

The irrealis is used to express certain kinds of generalities where the person making the statement thinks that it is generally true but knows they can be challenged on specific counter-examples. For example:

Ija Xafen nux kallas xilu.
The(DAT) Common go(NP.IM.IR) struggle-MOD learn.
Common is hard to learn.

The gloss is included there to illustrate how weird this kind of statement can be in Common. Where English would use an infinitive and a copula, Common lacks an infinitive or gerund and often will use dropped subject finite verbs like this instead. What this reads like is something like 'one struggle-ly would learn Common'. This is a common way of formulating general statements and takes some getting used to.

Notice, though, that the speaker is implicitly acknowledging that the statement is arguable or that there may be exceptions that prove the rule by using an irrealis verb. This is an extremely common rhetorical device and avoids counter-arguments that amount to quibbles.

Particular Hypothetical Statements

By this we mean statements which might be introduced with 'maybe' in English, or 'could be' statements where the 'could' doesn't indicate that some agent may be able to do something, just that a certain condition is possible.

A common mistake of English speakers is to calque the 'could' idiom into Common, like:

*A pikki si perat an citit.
The cat could be happy.

The sense the speaker is trying to achieve is 'maybe the cat is happy', but this structure using 'perat', 'to be able to', is not good, idiomatic Common. What you coud say is:

A pikki si an citit.

The simple irrealis is often sufficient to make a hypothetical statement. In idiomatic Common, a better way to signal that the intention is to present a hypothetical rather than responding to a 'hidden if' is to add a positive assertion marker to the verb:

A pikki si la an citit.

The meaning is identical, but the use of the 'la' modifier idiomatically signals the intent to make a hypothetical statement without an implied protasis.

Another way to signal a statement as hypothetical is to use the adverb 'olte', 'possible' to modify the main verb. In this case, the use of the irrealis is optional - using the realis signals that the speaker thinks the proposition is likely to be true. For example:

Olte, a pikki si an citit.

The use of the irrrealis in this version signals that the speaker is probably not very confident of the proposition but wants to assert that it could be true.

Polite Requests

The attached article on Greetings and Polite Speech goes into this in more detail. Basically, in order to make certain kinds of polite requests, you should place the verb in the irrealis, which makes it implicitly contingent on the addressee's choice to fulfill the request. The verb 'minna', 'request' iself is polite, but the irrealis would be used in the dependent clause describing the action requested. An example using a pure irrealis statement could be:

We nux jusal ijy kaffe.
I would like a coffee.

If the object of 'jusal' were a dependent clause and not a simple noun object, of course, an irrealis would be required in the dependent clause as well by the grammar of the language.

Future Statements

In Common, future statements can be expressed with certain helping verbs (see the article Helpers of Tense, Aspect and Mood, attached). It can also be expressed with a naked statement in the nonpast tense, where the future intention is clear from context, since future time is one possible meaning of this tense.

What many speakers will do for such simple, context-dependent future statements is to place them in the irrealis, especially if there is a degree of contingency and uncertainty to the statement. In general, use of the irrealis makes the statement more likely to be interpreted as a future statement. Example:

We nux stok ija Seáttyl.
I'm going to travel to Seatle.

In this hypothetical case, the speaker isn't expressing a 'hidden if' (although they could be, context is important), they have an absolute intention to travel to Seattle, but they are using the irrealis to express the future intention in order to hedge the certainty of the statement. Since the future is inherently uncertain, such forms have an inherent futurity.

Softening Chained Modal Verbs

Referring again to the attached article on Helpers of Tense, Aspect and Mood, the irrealis mood can be conbined with any of the periphrastic moods discussed there to soften or weaking the meaning. The implication of using the irrealis with a chained modal verb or modifier is that there may be a 'but' statement lurking somewhere.

In English, these forms are like 'should', or 'could' when describing ability to do something as opposed to an idiom for a hypothetical statement. Compare the statements:

We se riske hitaj.
I have to sleep.

We si riske hitaj.
I should sleep.

The latter is weaker, and may have an implied or actual 'joku' clause expressing a contrary condition explaining why the speaker isn't sleeping even though they should.