foster vs retard

foster

adj
  • Related by such care. 

  • Receiving such care. 

  • Providing parental care to children not related to oneself. 

noun
  • A foster parent. 

  • The care given to another; guardianship. 

verb
  • To cultivate and grow something. 

  • To nurture or bring up offspring, or to provide similar parental care to an unrelated child. 

  • To nurse or cherish something. 

retard

noun
  • Retardation; delay. 

  • A slowing down of the tempo; a ritardando. 

  • A person or being who is extremely stupid or slow to learn. 

verb
  • To put off; to postpone. 

  • To decelerate; to slow down. 

  • To keep delaying; to continue to hinder; to prevent from progressing. 

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