strong-willed vs tenacious

strong-willed

adj
  • Having a vigorous, independent will 

tenacious

adj
  • Unwilling to yield or give up; dogged. 

  • Having a good memory; retentive. 

  • Holding together; cohesive. 

  • Clinging to an object or surface; adhesive. 

How often have the words strong-willed and tenacious occurred in a corpus of books? (source: Google Ngram Viewer )