自転（じてん、jiten）
- rotation

The Japanese word 自転 (自転) primarily means "rotation" or "revolution," especially in the context of celestial bodies like planets. It can also refer to the act of rotating or revolving around an axis. The word emphasizes the movement of an object around its own internal center or axis. It's often used to describe the spinning motion of the Earth or a wheel.

⚫︎地球の自転 Translation: The Earth's rotation. ⚫︎車輪が自転する Translation: The wheel rotates. ⚫︎天体の自転と公転 Translation: Rotation and revolution of celestial bodies.

You would use 自転 when discussing the spinning or rotating motion of something, particularly things that rotate around a central point or axis. It is commonly used in scientific contexts (astronomy, physics), but also in everyday conversations when referring to wheels, fans, or other rotating objects.

⚫︎The word 自転 is typically written with the kanji 自 (ji - self, oneself) and 転 (ten - to revolve, to turn). ⚫︎The reading is じてん (jiten) in hiragana. ⚫︎There is no other common way to write this word, and the okurigana (hiragana suffixes) is not subject to variations.

⚫︎回転 (kaiten) - rotation, revolution ⚫︎旋回 (senkai) - circling, turning around ⚫︎公転 (kouten) - revolution (around a larger object, as opposed to 自転)

⚫︎There isn't a direct single antonym. ⚫︎Terms describing lack of movement or staying still, such as 静止 (seishi - standstill) or 停止 (teishi - stop), could be considered antonyms in a general sense.

地球は24時間で一回自転する。 ・Translation: The Earth rotates once every 24 hours. ・Explanation: This sentence explains the time it takes for the Earth to complete one rotation.

この機械の車輪は高速で自転している。 ・Translation: The wheel of this machine is rotating at high speed. ・Explanation: This sentence describes the spinning motion of a wheel.

The word 自転 is a compound word. 自 (ji) means "self" or "own," and 転 (ten) means "to turn" or "to revolve." Thus, the word literally means "self-rotation" or "to turn by oneself," which accurately describes the concept of rotation or spinning around one's own axis.