modal

modal.

1. adj. Que comprende o incluye modo o determinación particular.

2. adj. Perteneciente o relativo al modo gramatical.

3. m. pl. Acciones externas de cada persona, con que se hace notar y se singulariza entre las demás, dando a conocer su buena o mala educación. Era u. t. c. amb.
Fuente: Diccionario de la Real Academia Española

2. (Logic & Metaph.) Indicating, or pertaining to, some mode of conceiving existence, or of expressing thought, such as
the modes of possibility or obligation.
[1913 Webster +PJC]

3. (Gram.) Pertaining to or denoting mood. [PJC]

Modal Mo"dal(Gram.), n. A modal auxiliary.
[PJC]

modal auxiliary mo"dal aux*il"iar*y(Gram.), n. Any one of the auxiliary verbs of English, such as can, may,
will, shall, must, might, could, would, or should, which are
used together with the infinitive form of another verb to
express distinctions of mood[2], such as uncertainty,
possibility, command, emphasis, and obligation.
[PJC]

Source: The Collaborative International Dictionary of English