牽一髮而動全身

牵一发而动全身
qiānyīfàérdòngquánshēn
  1. lit. pulling a single hair makes the whole body move (idiom)
  2. fig. a small change in one part can affect the whole system

CEDICT

A slight change will affect everything else.

Wiktionary

更動一小部分，即影響全局

維基詞典

Entry Composition

1 牽 qiān
  1. to lead along
  2. to pull (an animal on a tether)
  3. (bound form) to involve
  4. to draw in
2 一髮 yīfà
  1. (literary, figurative) danger; dangerous moment
  2. (literary, figurative) distant and hazy
  3. (literary, figurative) something minute
  4. (literary, literal) a hair
  5. a hair
  6. danger; dangerous moment
  7. distant and hazy
  8. something minute
3 而 ér
  1. and
  2. as well as
  3. and so
  4. but (not)
  5. yet (not)
  6. (indicates causal relation)
  7. (indicates change of state)
  8. (indicates contrast)
4 動 dòng
  1. (of sth) to move
  2. to set in movement
  3. to displace
  4. to touch
  5. to make use of
  6. to stir (emotions)
  7. to alter
  8. abbr. for 動詞 dòngcí, verb
5 全身 quánshēn
  1. the whole body
  2. (typography) em