What does modal mean?

modality |mə(ʊ)ˈdalɪti|noun (pl.modalities)1 [ mass noun ] 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: the modalities of troop withdrawals.• a particular form of sensory perception: the visual and auditory modalities.(from oxford dictionary)