只知其一，不知其二

zhǐzhīqíyī,bùzhīqíèr
to know the first, but not know the second (idiom); only partial information

CEDICT

Entry Composition

=1 只 zhǐ only; merely; just
=1 只 zhǐ variant of 只 zhǐ
=1 只 zhǐ variant of 只 zhǐ
2 知 zhī
  1. to know
  2. to be aware
3 其一 qíyī
  1. one of the given (options etc)
  2. the first
  3. firstly
4 不知 bùzhī
  1. not to know
  2. unaware
  3. unknowingly
  4. fig. not to admit (defeat, hardships, tiredness etc)
5 其二 qíèr
  1. secondly
  2. the other (usu. of two)
  3. the second