知根知底 (zhī gēn zhī dǐ) — to know someone thoroughly / to be very familiar with someone's background

Definition

An idiom meaning you know someone thoroughly — their background, character, and history. Implies a long-standing, intimate familiarity, stronger than simply 认识.

idiom
to know someone thoroughly / to be very familiar with someone's background

Examples

  • ，知根知底。
    Wǒ men shì lǎo péng you le, hù xiāng zhī gēn zhī dǐ.
    We're old friends; we know each other inside out.
  • ，知根知底。
    Tā zài zhè jiā gōng sī gān le èr shí nián, duì měi gè yuán gōng dōu zhī gēn zhī dǐ.
    He's worked at this company for twenty years and knows every employee thoroughly.
  • ，知根知底，。
    Bié zài tā miàn qián sā huǎng, tā zhī gēn zhī dǐ, nǐ piàn bù liǎo tā.
    Don't lie in front of him — he knows you too well, you can't fool him.

Origin

Compound word
构词法gòucífǎ
联合liánhéSide by side

Two parts of equal weight, alike or opposite in meaning, standing side by side.

知根know the base
知zhīknow根gēnbase
动宾Verb + object
知底know the bottom
知zhīknow底dǐbottom
动宾Verb + object

知根 and 知底 together suggest knowing the base and the bottom of something.

Characters in this word

Two or more meaningful parts placed together so that their meanings combine into a new one.

An early form of 知 showed 大 (adult), 口 (mouth), and 子 (child): an adult speaking to a child to pass on knowledge. The 子 part was dropped, and the 大 part changed shape.

Open 知 →

Most characters — around four in five — are built this way: one part hints at the meaning, the other at the pronunciation.

Meaning part形符xíngfú
木木mù
Sound part声符shēngfú
艮
艮gèn根gēn(r)
Same sound today

根 pairs 木 (tree/wood), pointing to plant roots, with 艮 as a sound part.

Open 根 →

Two or more meaningful parts placed together so that their meanings combine into a new one.

An early form of 知 showed 大 (adult), 口 (mouth), and 子 (child): an adult speaking to a child to pass on knowledge. The 子 part was dropped, and the 大 part changed shape.

Open 知 →

Most characters — around four in five — are built this way: one part hints at the meaning, the other at the pronunciation.

Meaning part形符xíngfú
广广guǎngbuilding
Sound part声符shēngfú
氐
氐dī底dǐ
Same sound today

底 pairs 广 (building) with 氐, pointing to the bottom or foundation of a building. Some read 氐 as a bowing figure or tree root, adding a sense of 'down'.

Open 底 →

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