Translation guide
How to say 'become dirty' in Japanese depends on what is getting dirty and how. The most common way is to use the adjective 汚い (kitanai, 'dirty') with the verb なる (naru, 'to become'). There are also specific verbs for soiling, staining, or tarnishing.
To say that something becomes unclean or covered in dirt/grime.
The room became dirty.
My hands got dirty, so I'll wash them.
An intransitive verb meaning 'to become dirty/soiled'. Often implies a more noticeable stain or soiling, and can be used for clothes, surfaces, or reputation.
White shirts get dirty quickly.
The floor is dirty.
Same kanji but different reading. This is the transitive version 'to make dirty', but can be used in passive form 汚される to mean 'become dirty (by someone/something)'. Less common for simple state change.
This reading is often spiritual or metaphorical (defilement), not physical dirt.
One's heart becomes defiled.
To say that something gets a stain or spot from a specific substance.
To say that something becomes impure or harmful due to pollution.
To say that something loses its luster or becomes dull.
To say that someone accidentally dirties their clothes or body with excrement.
Literally 'to leak/let out'. Used for urinary or fecal incontinence. Often used in past tense 漏らした or 漏らしてしまった.
The child soiled his pants.
A euphemistic phrase meaning 'to have an accident' (especially toilet-related). More polite than 漏らす.
The elderly person had an accident.
汚くなる (kitanaku naru) is a general state change and can be used for anything becoming dirty. 汚れる (yogoreru) often implies a more noticeable soiling or staining, and is commonly used for clothes and surfaces. 汚くなる is more colloquial and flexible.
You cannot say 汚いなる. The adjective must be turned into an adverb: 汚くなる.
インクが布に染みた。
The ink stained the cloth.
海が油で汚れた。
The sea became dirty with oil.
金の指輪がくすんでしまった。
The gold ring became dull.