What does the word deviation mean?

Usage examples for deviation

  1. His remark is this: In the use of who as an interrogative, there is an apparent deviation from regular construction- it being used without distinction of case; as, 'Who do you speak to? – The Grammar of English Grammars by Goold Brown
  2. More will be gained by the observance of the ordinary laws of health, than by any foolish deviation, founded on ignorance. – The American Woman's Home by Catherine E. Beecher and Harriet Beecher Stowe