勾股定理 (gōu gǔ dìng lǐ) — Pythagorean theorem

Definition

The Chinese name for the Pythagorean theorem (a² + b² = c² in a right triangle). 定理 means 'theorem'; 勾 and 股 refer to the two legs and the hypotenuse in ancient Chinese geometry.

noun
Pythagorean theorem

Examples

  • 勾股定理。
    Wǒ men zài shù xué kè shàng xué le gōu gǔ dìng lǐ.
    We learned the Pythagorean theorem in math class.
  • 勾股定理。
    gōu gǔ dìng lǐ Shì shù xué zhōng yí gè zhòng yào de dìng lǐ.
    The Pythagorean theorem is an important theorem in mathematics.
  • 勾股定理。
    Lǎo shī yòng gōu gǔ dìng lǐ lái jiě zhè ge sān jiǎo xíng de wèn tí.
    The teacher used the Pythagorean theorem to solve this triangle problem.

Origin

Compound word
构词法gòucífǎ
偏正piānzhèngModifier + head

The first part narrows down the second: it says what kind of thing the head is.

勾股right-triangle sides
勾gōushort leg股gǔlong leg
联合Side by side
定理theorem
定dìngfixed理lǐprinciple
偏正Modifier + head

勾 and 股 name the two sides of a right triangle, while 定 and 理 give a fixed principle.

Characters in this word

No reliable origin is recorded for this character.

Open 勾 →

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

In 股, the left 肉 marks the body. The right side, now written 殳, comes from 夃, an old form for thigh, and gives the sound.

Open 股 →

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
宀宀mián
Sound part声符shēngfú
正
正zhèng定dìng
The sound has drifted apartThe sound part was a clue two thousand years ago — it often still helps, but not always.

定 is built from 宀 and 正, with 正 supplying the sound.

Open 定 →

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
玉玉yùjade
Sound part声符shēngfú
里
里lǐ理lǐ
Same sound today

理 pairs 玉 (jade) with 里, which shows how to say it; the jade part points to the old sense of polishing jade.

Open 理 →

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