(物体内的窟窿) cavity; void
									
										pulmonary cavity
										肺空洞
									
									
									
										Cavities in teeth are caused by decay.
										牙齿上的空洞是由龋蚀造成的。
									
									(无内容) empty; hollow; devoid of content; vague and general
									
										mere phrases; empty phraseology
										空洞的词句
									
									
									
										an article empty of matter
										内容空洞的文章
									
									
									
										make an inane remark
										作空洞的评论
									
									
									
										vague and general proposal
										空洞的议论
									
									(洞中发生的声音或回音的; 敲打空容器的声音) hollow
									
										a hollow voice
										空洞的声音