deontic modality

The order is: verb use→ability use (weak deontic modality)→deontic modality→epistemic modality.
这个顺序是:从动词的用法→表能力的用法(弱道义情态动词)→道义情态动词→知识情态动词。

In addition to these subjective uses, there is also an objective category of deontic modality, which merely predicates the existence of some necessity without actually committing the speaker to it.
还有些义务情态不表达说话者的态度，而仅仅说明某一必要性的现实存在，呈客观性。