Translation guide
To become worse in quality, condition, or value. Japanese uses different verbs depending on what is deteriorating and whether the change is gradual or sudden.
To say that something is getting worse over time, such as health, weather, economic conditions, or quality.
His condition deteriorated.
The weather is deteriorating.
Specifically refers to deterioration in quality, performance, or physical properties. Often used for materials, products, or abilities.
This plastic deteriorates in sunlight.
The battery's performance is deteriorating.
Means 'decline' or 'drop'. Used for measurable things like ability, quality, morale, or function. Emphasizes a decrease in level.
My concentration is deteriorating.
The standard of living deteriorated.
Refers to a gradual decline in strength, vitality, or power. Often used for physical or mental faculties, or the decline of nations.
My physical strength is deteriorating.
The country is deteriorating.
To describe something physically falling apart, rotting, or wearing out.
As above, but here emphasizes physical degradation of materials.
The rubber deteriorated and cracked.
Specifically means 'rot' or 'go bad', used for organic matter like food or wood.
Means 'decay' or 'crumble', often used for wood, buildings, or remains. Has a literary or poetic nuance.
To express that morals, standards, or society are getting worse.
悪化する is for abstract or general worsening (health, situation). 劣化する is for concrete quality degradation (materials, performance). Use 悪化する if unsure.
The relationship deteriorated.
The image quality deteriorated.
While 悪くなる (わるくなる) literally means 'become bad', it can sound childish or vague. Use specific verbs like 悪化する for formal or serious contexts.
果物が腐ってしまった。
The fruit deteriorated (rotted).
古い家が朽ちている。
The old house is deteriorating.
He leads a deteriorated (depraved) life.