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).

COMMON 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
general
Added 2026.6.7 11:04
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