Translation guide
The English word 'inert' describes something that lacks the ability to move, react, or take action. It can refer to physical stillness, chemical unreactivity, or a lack of energy/motivation. This guide helps you choose the right Japanese expression depending on whether you mean physically motionless, chemically inactive, or figuratively sluggish.
Describing an object, body, or substance that is not moving or cannot move on its own.
The most common and versatile way to say something is not moving. It's the negative form of 動く (to move).
その石はまったく動かない。
That stone is completely inert.
Means 'stationary' or 'at rest'. More formal or technical than 動かない.
静止した物体は、外力が加わらない限り動かない。
An inert object will not move unless an external force is applied.
Literally 'inactive'. Used in scientific contexts for inert gases or chemically inert substances, but can also describe physical inertness in technical writing.
不活性の物質は他の物質と反応しにくい。
Inert substances do not readily react with other substances.
Describing a substance that does not easily undergo chemical reactions.
The standard term for chemical inertness. Often used as a noun or na-adjective.
ヘリウムは不活性ガスです。
Helium is an inert gas.
Literally 'does not react'. A more descriptive phrase that can be used in everyday explanations.
金は酸素と反応しない。
Gold is inert to oxygen.
Means 'stable'. In chemistry, it implies low reactivity, but it's not a direct synonym for inert. Use with caution.
安定した can also mean emotionally stable or steady, so context is important.
この化合物は非常に安定している。
This compound is highly inert.
Describing a person, group, or system that shows no initiative, motivation, or activity.
Means 'lethargic' or 'apathetic'. Describes a lack of mental or physical energy.
彼は無気力で、一日中ソファに寝ていた。
He was inert and lay on the sofa all day.
Literally 'has no vitality'. Used for people, places, or organizations that seem dull or lifeless.
その会議は活気がなく、誰も発言しなかった。
The meeting was inert; no one spoke up.
Means 'stagnant'. Often used for economies, projects, or situations that are not progressing.
経済が停滞している。
The economy is inert.