i was taught that verbs are either transitive or intransitive.
but what kind of verb is 分かる ?
WWWJDIC lists it as intransitive.
Yet the replies/comments from this thread Why is it 日本語がわかります instead of 日本語をわかります? argues that を can be used with 分かる.
so is 分かる both a transitive verb and an intransitive verb at the same time?
A general answer: The definition of intransitive is the negation of transitive. Logically, a verb is either intransitive or transitive; there is no other possibility. You may say that a verb becomes either of them depending on its usage, but a verb is never "neither intransitive nor transitive".
In this particular case, を is not allowed in the kind of construction mentioned in standard way of speaking. If you actually see it, then it is either wrong, or the speaker has a different lexical entry for the verb. These are called idiolect. Simply put, those people are speaking a "different language". In that case, you can say that the verb in question is either intransitive or transitive depending on the idiolect.
To answer Lukman's question: Many transitive verbs can be used intransitively with a specifically implied object. For example, Japanese 飲む or English drink is a transitive verb:
ジュースを飲んだ。
I drank juice.
But you can turn it into an intransitive verb by omitting the object and implying a specific object, in this case 'alcohol':
昨日は朝まで飲んだ。
I drank overnight yesterday.
i was taught that verbs are either transitive or intransitive.
That is unfortunate, because the claim is misleading as long as Japanese is concerned.
Unlike English, Japanese does not have a strict distinction between transitive and intransitive verbs. Although some people categorize the verbs which can be used with ～を as transitive verbs and the other verbs as intransitive verbs, ～を is just one of the modifiers of a verb in the same way as ～に and ～から, and these modifiers are optional.
In these sentences, are 食べる and 飲む transitive verbs with ～を modifiers omitted, or intransitive verbs? I cannot see any point distinguishing these two.
So in Japanese, classifying all verbs to either transitive and intransitive does not have much use.
What is useful is the transitive-intransitive correspondence such as 動かす and 動く. Note that even in this case, 動かす can be used without an ～を modifier.
わかる usually takes ～が when specifying what is understood, but ～を is also used in some contexts, as stated in the page which you linked to. One can describe this as “わかる is usually used as an intransitive verb, but can sometimes also be used as a transitive verb,” but I do not think that this explanation makes the situation any easier to understand.
The following analysis is a paraphrase of the discussion in "Japanese: A linguistic introduction", Hasegawa, 2015
One can consider three classes of predicates when it comes to transitivity. One class is verbs that come in clear transitive / intransitive pairs:
ミドリが扉を開けた。 midori opened the door.
扉が開いた。 the door opened.
in these pairs, the patient (the noun that something happens to) is marked by を with the transitive verb, (it is marked as the object of the sentence), and が with the intransitive verb, (it is marked as the subject of the sentence). This is the vast majority of Japanese verbs. Note that even if the が marked NP is omitted from a sentence containing a transitive verb it is still understood to be there.
ビールを飲んだ。 X drank the beer. / NOT: the beer was drunk.
There is also a small class of verbs that, like most english verbs, can be used transitively or intransitively:
ミドリが扉を開いた。 midori opened the door.
扉が開いた。 the door opened.
(note this verb is not aku /akeru, but hiraku and is in the same form in both the above sentences)
The third situation (the one that 分かる) falls under, is the situation of low transitivity. This is the situation in which the patient is not really affected by the action (the analysis is more complicated than that, they list 10 things that affect transitivity, but thats the main thing). So the answer to your question is that different Japanese linguists have analyzed the situations differently.
One camp says that が absolutely marks the subject of any sentence so a sentence like:
日本語が分かる。 = Japanese (subject) is understandable.
This analysis is compelling because it keeps the particle usage consistent (が marks subject). But that would mean that 分かる would behave like an intransitive verb (not taking an object in its normal usage). But the problem with this is as you have noted, there are times that 分かる does take を, and additionally, most people's perception is that "to understand" is a transitive action, i.e. There is an "agent" "understanding" something.
Others (most notably Kuno "The structure of the Japanese Language", 1973) have argued that in "日本語が分かる", が marks the direct object. He goes on to argue that a certain class of predicates (sensory perception, want-to-do verbs, can-do-verbs) can mark their object with が instead of を. This interpretation analyzes 分かる as a transitive verb, but one that has a non-standard particle usage (marking it's object with が). The advantage of this analysis is that it maintains our perception of the transitivity of "to understand", it also accounts for the ability of the verb to mark it's object in the "normal" way in addition to が.
Both analyses have their advantages and disadvantages.
Hasegawa argues that the core issue is the perceived (by the speaker) transitivity of these verbs. The lower the transitivity, the more likely their "object" (in the Kuno analysis) is to be marked by が.
As an example she offers the following:
わたしは ビール が/を 飲みたい。 I want to drink beer.
わたしは 部長 が/を 殺したい。 I want to kill (my) section chief.
She says that most native speakers would prefer が in the first case, but in the case of a very highly transitive verb (to kill), the preference for を marking increases and that most native speakers would prefer を in the second sentence.
It is important to note though that what is going on here is that there are some verbs (sensory perception, want to, can do, to say, to meet) that don't fit neatly into the transitive/intransitive framework. All these verbs share the characteristic of being "low transitivity".
What is absolutely not true, though, is the notion that transitivity is not a semantic feature of Japanese. The transitive / intransitive distinction is taught in 国語文法 (the school grammar that Japanese kids are taught). Additionally, Old Japanese is analyzed as having transitivity (and transitivity reversing) morphemes as part of the verb structure (that is why the transitive/intransitive pairs follow patterns). And those transitivity distinctions have been traced through the language to middle japanese, then late, then modern, to arrive at the currently used verb forms.
Japanese kids are taught about transitivity using the same trick that they teach english speaking kids. "can you ask the question 何を?".
Even with pro-drop, if some one says:
わたしは 飲みました。
you can ask:
何を飲みました？。
not stating objects doesn't change the valence of the verb. It is still understood to have an object (i.e. you can ask about it).
By the same token the sentence:
何を開いた？
would be rejected by native speakers as being ungrammatical.
So, we have two classes of verbs, 自動詞 and 他動詞, the so-called intransitive and transitive.
The problem lies in the absence of mapping between the grammatical notions in both languages. I believe that you can be transitive and 自動詞. The only difference is that the particle used for the object will be が instead of を.
For me, the verb 分かる is a transitive 自動詞, the verb 開く is an intransitive 自動詞, and the verb 食べる is a transitive 他動詞. I can't think of any intransitive 他動詞.
