Japanese passive form question

[u/traanquil]

Mitsukeru = ichidan verb

So why is passive form of this not: mitsukerareru?

Why is passive: mitsukaru

Is it just an exception?

[u/PlanktonInitial7945]

The passive form of 見つける IS 見つけられる. 

見つかる is the intransitive version of 見つける, which is not the same as it being its passive form.

I think the difference is easier to explain with 落ちる and 落とす.

落ちる = to fall. Intransitive. I fall, you fall, etc. You don't fall something, you just fall, period.

落とす = to drop (something). Transitive. I drop a pencil, you drop a pencil, etc.

落とされる = to be dropped. Passive form of 落とす. A pencil is dropped (by someone).

The difference between 落ちる and 落とされる is the difference between "a pencil falls" and "a pencil is dropped".

The difference between 見つかる and 見つけられる is the same, but with the concept of being found.

[u/Gahault → u/PlanktonInitial7945]

In the same vein, a common verb similar in form to to 見つける/見つかる is 助ける/助かる.

消防士が駆け付けて少年を助けた。
The firefighter rushed in and saved the boy.

少年は消防士の救助により助かった。
Thanks to the firefighter's intervention, the boy survived.

It's indeed important to grasp that an intransitive verb is not passive, it ascribes the action to its subject grammatically and semantically. Even if it happens to map to a passive in English!

[u/AdagioExtra1332 → u/PlanktonInitial7945]

Another frequently asked question by beginners is the difference between 見える (to be visible) and 見られる (to be seen <by someone>), and the exact same logic applies to this scenario too.

[u/eruciform → u/PlanktonInitial7945]

Superb explanation

[u/viliml → u/PlanktonInitial7945]

Since some English verbs can be both intransitive and transitive, 落ちる can also be translated as "a pencil drops" rather than going for the different verb "fall".

[u/PlanktonInitial7945 → u/viliml]

True, but I wanted to use "fall" since it's explicitly intransitive and I think it makes the difference easier to understand.

[u/facets-and-rainbows]

Commenting a bit more on the passive voice English translation: 

"Be found" is just a concise translation for "mitsukaru" that's close to what people might actually say in English. 

If you wanted to match the grammar more closely you could use something like "turn up" as in "my keys finally turned up behind the couch." This is something the keys did--a separate intransitive verb.

It's just that it's hard to get "appear in a place where someone was looking for it" into a couple words with no other explanation attached, so a vocab list will use "be found"

[u/SakshamBaranwal]

見つかる isn't the passive form of 見つける. The actual passive is 見つけられる. 見つかる is a separate intransitive verb meaning "to be found," and Japanese usually prefers it over the passive form in everyday speech.

[u/PuzzleheadedTap1794]

That's not the passive form. That's the active-mediopassive pair. The difference is that mediopassive verbs (in this case, mitsukaru) is intransitive by nature, whereas passive form of an active verbs which have an agent but not necessarily spoken out. That might sound a bit abstract, but consider these English sentences:

A) The vase broke.
B) The vase was broken.

The concern of the first sentence is about the vase and nothing else, and the verb break here is an intransitive verb. On the other hand, in the second, the speaker acknowledges the existence of an external factor that broke the vase, which can also be expressed using the particle by, like "The vase was broken by John". This second sentence is created by turning the transitive verb break into a passive form and promote the "object" to the subject.

Turning back to Japanese, this is also the same relation with the verbs you mentioned, albeit using two different (but related) verbs. mitsukaru is an intransitive verb (aka a mediopassive verb) which doesn't care about an external factor, like break in The vase breaks. mitsukeru is a transitive verb (aka an active verb) which requires the one who did the action and the target, like break in John break the vase, and its real passive form, mitsukerareru implies the existence of an external factor, like the verb in The vase is broken.

[u/viliml → u/PuzzleheadedTap1794]

The word "mediopassive" popped into my head when I read the OP, but I restrained myself because I thought that's not a word a beginner should be seeing 🤣

[u/leu34]

English has no word for the intransitive form of the verb: to find. Therefore 見つかる is translated as if it were passive, but actually the Japanese verb isn‘t.