A realis mood is a grammatical mood which is used principally to indicate that something is a statement of fact; in other words, to express what the speaker considers to be a known state of affairs, as in declarative sentences. Most languages have a single realis mood called the indicative mood, although some languages have additional realis moods, for example to express different levels of certainty. By contrast, an irrealis mood is used to express something that is not known to be the case in reality.