Deontic modality (abbreviated DEO) is a linguistic modality that indicates how the world ought to be according to certain norms, expectations, speaker desire, etc. In other words, a deontic expression indicates that the state of the world (where 'world' is loosely defined here in terms of the surrounding circumstances) does not meet some standard or ideal, whether that standard be social (such as laws), personal (desires), etc. The sentence containing the deontic modal generally indicates some action that would change the world so that it becomes closer to the standard or ideal.
- Commissive modality (the speaker's commitment to do something, like a promise or threat): "I shall help you."
- Directive modality (commands, requests, etc.): "Come!", "Let's go!", "You've got to taste this curry!"
- Volitive modality (wishes, desires, etc.): "If only I were rich!"
Realisation in speech
However, many languages (like English) have additional ways to express deontic modality, like modal verbs ("I shall help you.") and other verbs ("I hope to come soon."), as well as adverbials (hopefully) and other constructions.
Esperanto has a mood called volitive which is really a generic deontic mood, expressing commands as well as will, desire, and purpose. It is formed by adding -u to the verb stem.
- Estu feliĉa! "May you be happy!" / "Be happy!"
- Donu al mi panon. "Give me bread!"
- Ni iru! "Let's go!"
- Mi legu tion. "Let me read that."
- Loos, Eugene E.; Susan Anderson; Dwight H. Day, Jr.; Paul C. Jordan; J. Douglas Wingate. "What is deontic modality?". Glossary of linguistic terms. SIL International. Retrieved 2009-12-28.
- Bhat, D. N. Shankara (1999). The prominence of tense, aspect, and mood. John Benjamins Publishing. ISBN 90-272-3052-8.
- Loos, Eugene E.; Susan Anderson; Dwight H. Day, Jr.; Paul C. Jordan; J. Douglas Wingate. "What is commissive modality?". Glossary of linguistic terms. SIL International. Retrieved 2009-12-28.
- Palmer, F.R., Mood and Modality, Cambridge University Press, 2001, p. 70 ff.
- Fryer, Helen. The Esperanto Teacher (10th ed.). Project Gutenberg. Retrieved 2010-03-13.