affect vs alter

affect

verb
  • To influence or alter. 

  • To make a show of; to put on a pretense of; to feign; to assume. To make a false display of. 

  • To feel affection for (someone); to like, be fond of. 

  • To burden (property) with a fixed charge or payment, or other condition or restriction. 

  • To move to emotion. 

  • Of an illness or condition, to infect or harm (a part of the body). 

noun
  • A subjective feeling experienced in response to a thought or other stimulus; mood, emotion, especially as demonstrated in external physical signs. 

alter

verb
  • To change the form or structure of. 

  • To castrate, neuter or spay (a dog or other animal). 

  • To tailor clothes to make them fit. 

  • To become different. 

  • To affect mentally, as by psychotropic drugs or illness. 

noun
  • An identity or headmate of a person with dissociative identity disorder (previously known as multiple personality disorder). A member of a system. 

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