fragile vs progressive tense

fragile

noun
  • Something that is fragile. 

adj
  • Easily broken or destroyed, and thus often of subtle or intricate structure. 

  • Feeling weak or easily disturbed as a result of illness. 

  • Thin-skinned or oversensitive. 

progressive tense

noun
  • Synonym of continuous tense. 

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