assert vs explain

assert

verb
  • To declare with assurance or plainly and strongly; to state positively. 

  • He would often assert that there was life on other planets. 

  • To maintain or defend, as a cause or a claim, by words or measures; to vindicate a claim or title to 

  • To insist on the legitimacy of one's rights, opinion, etc; not to allow oneself to be dismissed; to ensure that one is taken into consideration; to make oneself respected; to be assertive. 

  • To use or exercise and thereby prove the existence of. 

  • To set a signal on a line using a voltage or electric current. 

  • To specify that a condition or expression is true at a certain point in the code. 

noun
  • an assertion; a section of source code which tests whether an expected condition is true. 

explain

verb
  • To make plain, manifest, or intelligible; to clear of obscurity; to illustrate the meaning of. 

  • To give a valid excuse for past behavior. 

  • To make something plain or intelligible. 

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