GbEng
质量密集月球上的阴暗部，其内部岩石比周围地区的岩石的密度大，因此产生略大些的引力 A mare on the moon having rock of greater density than that of the surrounding area, thus exerting a slightly higher gravitational force.
模态逻辑命题的限制条件，建立在其内容的肯定或否定其可能性，不可能性，偶然性或必然性基础之上 The classification of propositions on the basis of whether they assert or deny the possibility, impossibility, contingency, or necessity of their content.