cavity
n.
1540s, from Middle French cavité (13c.), from Late Latin cavitatem (nominative cavitas) "hollowness," from Latin cavus "hollow" (see cave, n.).
〔李〕[cav =hollow中空的；-ity ⇒“the condition or fact of be-ing hollow中空之状况或事实”→] n. a hollow place；hole中空；洞
〔李〕[cav;-ityn.] n.洞； 中空 ←cav (L cavus)=hollow 凹陷