olemus
Wiktionary:
1. an unintended consequence of any action in addition to the intended consequence of that action
2. (medicine) an adverse effect, an unintended consequence of a drug or therapy; usually not a beneficial effect
3. (computing) a change in state caused by a function call (typically "side-effect")
The Eiffel programming language is somewhat purist in insisting that functions have no side effects.

ülevaateid
https://en.wikipedia.org/wiki/Side_effect_(computer_science)