Deontic modality (abbreviated DEO) is a linguistic modality that indicates how the world ought to be according to certain norms, expectations, speaker desires, 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.
This category includes the following subcategories:
- Commissive modality (the speaker's commitment to do something, like a promise or threat; alethic logic or temporal logic would apply): "I shall help you."
- Directive modality (commands, requests, etc.; deontic logic would apply): "Come!", "Let's go!", "You've got to taste this curry!"
- Volitive modality (wishes, desires, etc.; boulomaic logic would apply): "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 formally called volitive which is also used for various directive uses, so it can be seen as a broader deontic mood. However, it is not used to express commissive modality. It is formed by adding -u to the verb stem, and it is used for orders and commands as well as for expressing will, desire, and purpose.
- Estu feliĉa! "(May you) Be happy!"
- Donu al mi panon. "Give me bread."
- Ni iru! "Let's go!"
- Mi legu tion. "Let me read that."
- Mi volas, ke vi helpu min. "I want you to help me."
- Ĉu mi faru tion? "Shall I do that?"
- Loos, Eugene E.; Susan Anderson; Dwight H. Day, Jr.; Paul C. Jordan; J. Douglas Wingate. "What is a 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 a 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. "Lesson 10". The Esperanto Teacher (10th ed.). Project Gutenberg. Retrieved 2021-05-26.