牵一发而动全身

牽一髮而動全身
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

更动一小部分，即影响全局

維基詞典

Entry Composition

1 牵 qiān
  1. to lead along
  2. to pull (an animal on a tether)
  3. (bound form) to involve
  4. to draw in
=2 一发 yīfā
  1. along with all others; altogether
  2. even more
=2 一发 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 动 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 动词 dòngcí, verb
5 全身 quánshēn
  1. the whole body
  2. (typography) em