円周率(えんしゅうりつ)

えんしゅうりつ
noun
pi; ratio of circumference to diameter
number
1. pi (π); ratio of a circle's circumference to its diameter
The mathematical constant pi (π), approximately 3.14159, representing the ratio of any circle's circumference to its diameter.
円周率(えんしゅうりつ)は約(やく)3.14だ。
Pi is approximately 3.14.
円周率(えんしゅうりつ)を100桁(けた)まで覚(おぼ)えている。
I have memorized pi to 100 digits.
円(えん)の面積(めんせき)は半径(はんけい)の二乗(にじょう)に円周率(えんしゅうりつ)をかけて求(もと)める。
The area of a circle is found by multiplying the square of the radius by pi.

Composed of 円(えん) (circle) + 周(しゅう) (circumference) + 率(りつ) (ratio). The Greek letter π is read パイ in Japanese.

Common collocations

  • 円周率(えんしゅうりつ)を使(つか)う: to use pi
  • 円周率(えんしゅうりつ)の近似値(きんじち): an approximate value of pi
  • 円周率(えんしゅうりつ)を覚(おぼ)える: to memorize pi

Cultural note

Japanese students typically learn 3.14 as a working value. March 14 (3/14) is celebrated as 円周率(えんしゅうりつ)の日(ひ) (Pi Day).

general
Added 2026.6.5 12:07 · Revised 2026.9.2 13:02
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