lack vs weakness

lack

noun
  • A deficiency or need (of something desirable or necessary); an absence, want. 

verb
  • To be short (of or for something). 

  • To be without, not to have, to need, to require. 

weakness

noun
  • A special fondness or desire. 

  • An inadequate quality; fault 

  • The condition of being weak. 

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