球(きゅう)

きゅう

noun

sphere; ball (geometric)

1. sphere; ball (geometric)

A sphere in the geometric sense — a perfectly round three-dimensional shape. Used in math, science, and the names of round objects. Distinct from ボール, which refers to balls used in sports.

球(きゅう)の体積(たいせき)を計算(けいさん)する。

Calculate the volume of a sphere.

地球(ちきゅう)は完全(かんぜん)な球(きゅう)ではない。

The Earth is not a perfect sphere.

半径(はんけい)が倍(ばい)になると、球(きゅう)の表面積(ひょうめんせき)は四倍(よんばい)になる。

When the radius doubles, the surface area of a sphere becomes four times larger.

Single-character noun used in geometry and as the building block of many compounds. In ordinary speech a round object is more often ボール (sports ball) or 玉(たま) (small round thing).

Compounds

地球(ちきゅう): Earth ("earth-sphere")
野球(やきゅう): baseball
電球(でんきゅう): light bulb
半球(はんきゅう): hemisphere
球体(きゅうたい): a sphere (the abstract shape)
球面(きゅうめん): spherical surface

Similar words

ボール: ball (sports, toys) — everyday word for a ball you can throw or kick
玉(たま): bead; small ball; bullet — everyday small round things

Related Words

Compare: ボール (ball)

Compare: 玉(たま) (bead)

Related: 円筒(えんとう) (cylinder)

Related: 直径(ちょっけい) (diameter)

Related: 立方体(りっぽうたい) (cube)

Related: 円錐(えんすい) (cone)

Related: 円柱(えんちゅう) (cylinder)

general

Added 2026.6.7 11:04 · Revised 2026.9.30 21:23

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