Translation guide
Describes something that is defective, not working correctly, or has a flaw. Covers physical objects, reasoning, and systems.
The most common meaning: a product, device, or part that has a defect and does not function as intended.
Standard way to say a machine or device is broken/out of order. Emphasizes the state of not working.
この洗濯機は故障している。
This washing machine is faulty.
Describes an argument, logic, or reasoning that is unsound or contains errors.
Directly modifies nouns like 論理 (logic) or 推論 (reasoning).
それは欠陥のある論理だ。
That's faulty logic.
Describes memory or senses that are unreliable or inaccurate.
Literally 'memory is vague'; natural way to say memory is faulty/unreliable.
その日のことは記憶があいまいだ。
My memory of that day is faulty.
The English word 'faulty' covers many nuances. Do not use a single Japanese word for all cases. Choose based on context: physical defects vs. abstract flaws.
A defective product; used as a noun. Common in consumer contexts.
それは不良品だったので、返品した。
It was faulty, so I returned it.
More formal; 'has a defect/flaw'. Used for products, designs, or systems.
この車には欠陥がある。
This car is faulty.
Common in technical/business contexts; 'has a malfunction/glitch'. Softer than 欠陥.
ソフトウェアに不具合がある。
The software is faulty.
Means 'mistaken/erroneous'. Common for incorrect reasoning.
彼の議論は誤った前提に基づいている。
His argument is based on a faulty premise.
Means 'illogical/incoherent'. Emphasizes lack of logical flow.
その説明は筋の通らないものだった。
The explanation was faulty.
Means 'memory is uncertain/unreliable'. Slightly more formal.
目撃者の記憶は不確かだった。
The witness's memory was faulty.