annotation vs impressions

annotation

noun
  • Information relating to the genetic structure of sequences of bases. 

  • A critical or explanatory commentary or analysis. 

  • Metadata added to a document or program. 

  • A comment added to a text. 

  • The process of writing such comment or commentary. 

impressions

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