noun
butterfly effect
Technical term from chaos theory; describes how a small change can lead to large-scale, unpredictable consequences.
バタフライ効果とは、蝶の羽ばたきが遠くの天気を変えるという考え方だ。
The butterfly effect is the idea that a butterfly's flapping wings could change the weather far away.
Loanword from English 'butterfly effect', combined with 効果 (effect).