Translation guide
How to express that someone or something cannot be recognized, identified, or is no longer identifiable in Japanese.
The speaker cannot identify someone or something by sight, often due to change, damage, or disguise.
Common phrase meaning 'cannot tell apart' or 'cannot distinguish'. Used when something is so changed or similar that you cannot identify it.
彼は変装していて、見分けがつかなかった。
He was in disguise and I couldn't recognize him.
この写真、ぼやけていて誰だか見分けがつかない。
This photo is so blurry I can't tell who it is.
Literally 'don't know who it is'. Natural for not recognizing a person.
マスクをしていて、誰だかわからなかった。
He was wearing a mask, so I couldn't tell who he was.
For objects: 'can't tell what it is'.
その物体は何だかわからなかった。
I couldn't tell what that object was.
More formal/literary: 'cannot distinguish/judge'. Used in technical contexts.
損傷がひどく、機種の判別ができなかった。
The damage was so severe that the model could not be identified.
Even if I look, I can't tell. Emphasizes visual inability.
この文字、見てもわからない。
I can't make out these characters even when I look at them.
Something or someone has changed so much that they are no longer recognizable as their former self.
Idiomatic: 'not a shadow of one's former self'. Used for drastic negative change in appearance or condition.
彼は病気で見る影もなかった。
He was unrecognizable due to illness.
Literally 'does not retain its original form'. Used for objects or scenes that are completely destroyed or altered.
事故で車は原形をとどめていなかった。
The car was unrecognizable after the accident.
Has completely changed. Softer than the above, can be positive or negative.
故郷はすっかり変わってしまって、わからなかった。
My hometown had changed so much I didn't recognize it.
No trace of the former appearance. Poetic/literary nuance.
昔の面影はどこにもなかった。
There was no trace of the person I once knew.
The identity of someone or something is completely unknown; cannot be determined.
Specifically for a person whose identity is unknown.
身元がわからない遺体が見つかった。
An unidentifiable body was found.
Noun/na-adjective: 'identity unknown'. Often used for mysterious creatures, UFOs, etc.
正体不明の生物が目撃された。
An unidentifiable creature was sighted.
Don't know who/what kind of person. Slightly dramatic.
彼が何者かわからない。
I have no idea who he is.
Cannot recognize by sound, voice, or other non-visual means.
Can't tell by voice.
電話では声が変わっていて、誰だかわからなかった。
His voice sounded different on the phone, so I couldn't tell who it was.
Cannot distinguish by hearing.
雑音でアナウンスが聞き分けられなかった。
I couldn't make out the announcement because of the noise.
There is no single Japanese adjective that directly corresponds to 'unrecognizable' in all contexts. Instead, use phrases like 見分けがつかない or 誰だかわからない depending on the situation.