side affect

Noun

side effect (plural side effects)

1. An unintended consequence, or secondary result, of any action, in addition to the main or intended consequence of that action.
   • The processing of certain raw materials - pulp and paper, oil, and alumina, for example - can have substantial environmental side effects.1987, Brundtland Report

   Synonyms:

   by-product

   1. An unintended consequence of a drug or therapy; usually an adverse effect, and not a beneficial one.
      • “While all pharmaceutical treatments have side effects, racism is not a known side effect of any Sanofi medication.”2018 May 30, Christine Hauser, quoting Sanofi, “Roseanne Barr’s Ambien Defense Is Disputed: ‘Racism Is Not a Known Side Effect’”, in The New York Times, →ISSN
   2. A change a in state outside of the local environment of the function being called.
      • The Eiffel programming language is somewhat purist in insisting that functions have no side effects.