Modality is the expression of information about the attitude of a language user towards the validity of the content of a proposition. Possibility, probability, obligation, permission, prohibition, necessity, and ability are examples of notions of modality. Modality markers are used to express these notions. The typical modals in TİD are: have_to, maybe, obliged_to, necessary, forbidden and permıtted. These are used predicatively in TİD.
Modality is categorized into two: deontic and epistemic modality.