n.
-ries 情态助动词

[ noun ]
an auxiliary verb (such as `can' or `will') that is used to express modality
<noun.communication>

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]