1. The fact, state, or quality of being modal.

2. A tendency to conform to a general pattern or belong to a particular group or category.

3. Logic The classification of propositions on the basis of whether they assert or deny the possibility, impossibility, contingency, or necessity of their content. Also called mode.

4. modalities The ceremonial forms, protocols, or conditions that surround formal agreements or negotiations: "[He] grew so enthusiastic about our prospects that he began to speculate on the modalities of signing" (Henry A. Kissinger).

5. Medicine A therapeutic method or agent, such as surgery, chemotherapy, or electrotherapy, that involves the physical treatment of a disorder.

6. Physiology Any of the various types of sensation, such as vision or hearing.