MODALITY. In syntactic and semantic analysis, a term chiefly used to refer to the way in which the meaning of a sentence or clause may be modified through the use of a MODAL VERB, such as may, can, will, must. In a wider sense, the term is used to cover linguistic expression of these concepts other than through the modal auxiliaries: ‘It will possibly rain later this evening’; ‘I am sure that the plane has landed by now’; ‘You have my permission to smoke now’; ‘I am obliged to go.’ Adverbs such as possibly, perhaps, probably, certainly have been called modal adverbs, and such adjectives as possible have been called modal adjectives. The term is also extended to include the subjunctive mood and the past verb forms used to express hypothetical meaning (that is, that the situation is unlikely to occur or has not occurred): ‘I wish I knew her’; ‘If I saw him, I would recognize him’; ‘If you had said that, I would not have minded.’ In case grammar, modality refers to one of the two underlying constituents of sentence structure (the other being proposition). The modality includes those features that relate to the sentence as a whole, such as tense and negation.

mo·dal·i·ty / mōˈdalitē/ • n. (pl. -ties) 1. modal quality: the harmony had a touch of modality.2. a particular mode in which something exists or is experienced or expressed. ∎  a particular method or procedure: they addressed questions concerning the modalities of Soviet troop withdrawals. ∎  a particular form of sensory perception: the visual and auditory modalities. ∎ (in medicine, particularly homeopathy) a symptom or pattern that aids in diagnosis: The modality of "worse with activity" is associated with Rhus Tox.

modality (moh-dal-iti) n.
1. a form of sensation, such as smell, hearing, tasting, or detecting temperature.

2. one form of therapy as opposed to another, such as the modality of physiotherapy contrasted with that of radiotherapy.