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未知数 (wèi zhī shù) — (mathematics) unknown quantity; an unknown; something uncertain or unpredictable

Definition

Literally 'unknown number' — its math sense (a variable in an equation) extends metaphorically to 'an unknown factor' (a person or outcome you can't predict). Unlike 不得而知, it names the unknown thing itself, not the inability to find out.

noun
(mathematics) unknown quantityan unknownsomething uncertain or unpredictable
Measure word · 个

Examples

  • 未知数。
    Jiě zhè ge fāng chéng yào zhǎo chū liǎng gè wèi zhī shù.
    To solve this equation, you need to find two unknowns.
  • 未知数。
    Zhè cì kǎo shì de chéng jì hái shì gè wèi zhī shù.
    The result of this exam is still an unknown.
  • 未知数，。
    Chuàng yè lù shang chōng mǎn wèi zhī shù, yào zuò hǎo zhǔn bèi.
    The road to starting a business is full of unknowns; you need to be well prepared.

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.

未知unknown
未wèinot知zhīknow
偏正Modifier + head
数shùnumber

未知 means not yet known, and 数 is a number, so it is an unknown quantity.

Characters in this word

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

The shape 未 shows a tree with extra branches spreading above its trunk, like lush, overlapping limbs.

Open 未 →

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.

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 →
Appears in
HSK 3.0 Level 7-9Math

Browse more HSK 7-9 words or search the full 43,000-word dictionary.