A fear of offending people has led to the replacement of many negative expressions with more positive alternatives, with the adjective challenging being a prime example. The Oxford English Corpus shows that it is used euphemistically for difficult or trying and applied to unpleasant situations （a challenging period of slowing growth and rising unemployment）, troublesome individuals （it's surprising how common it is for parents to encounter challenging behaviour with their teenagers）, and even avant-garde music （the opera's challenging atonal score）. See also ISSUE.