cavity vs vacuity

cavity

noun
  • A hollow area within the body. 

  • A hole or hollow depression in a solid object. 

  • A small or large hole in a tooth caused by caries; often also a soft area adjacent to the hole also affected by caries. 

vacuity

noun
  • Physical emptiness, an absence of matter; vacuum. 

  • Idleness; listlessness. 

  • Emptiness. 

  • An empty or inane remark or thing. 

How often have the words cavity and vacuity occurred in a corpus of books? (source: Google Ngram Viewer )