无理数 (wú lǐ shù) — irrational number (math)

Definition

noun
irrational number (math)

Examples

  • 无理数。
    Zhè ge shù shì yí gè wú lǐ shù.
    This number is an irrational number.
  • π无理数。
    Yuán zhōu lǜ π shì wú lǐ shù.
    Pi is an irrational number.
  • 无理数。
    Wǒ men zài shù xué kè shàng xué guò wú lǐ shù.
    We studied irrational numbers in math class.

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.

无理without reason
无wúwithout理lǐreason
动宾Verb + object
数shùnumber

无理 means without reason, and 数 is number, so it names an irrational number.

Characters in this word

A drawing of the thing itself, worn down over three thousand years into a few strokes.

This origin belongs to the traditional form 無; 无 is its simplified writing.

For the simplified 无, the story is about 無. 無 drew a person dancing with ox tails held in both hands to pray for rain, then was borrowed for 'have no', so the picture does not explain that meaning.

Open 无 →

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 →

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

This origin belongs to the traditional form 數; 数 is its simplified writing.

Meaning part形符xíngfú
攴攴pū
Sound part声符shēngfú
婁
婁lóu數shù(r)
The sound has drifted apartThe sound part was a clue two thousand years ago — it often still helps, but not always.

The traditional form 數 pairs 攴, the meaning part, with 婁, the sound part; the simplified 数 is a shorthand.

Open 数 →

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