I've been having quite a bit of trouble with this particular verb. according to rikaichan they can both be transitive or intransitive, so that's not the issue. The other option is that they are used to open different things, like rikaichan suggests. But I know I've heard both あく and ひらく when referring to a door. So I'm really confused with how they are used.

For these sort of very specific questions, googling in Japanese is helpful. http://detail.chiebukuro.yahoo.co.jp/qa/...1158560511

It seems similar questions have been asked multiple times on this forum, e.g., here.

Here's what I wrote about how to know if 開く is ひらく or あく:

magamo Wrote:Basic words tend to have many different meanings and usages, and overlap/similarity in meaning between different words can cause ambiguity in reading.

I looked up ひらく (開く) in my J-J dictionary, only to get struck with 34 different meanings. The explanation of one meaning says, "Often it is difficult or requires furigana to know whether it is ひらく or あく if this meaning is used with kanji." The other 33 meanings may not confuse native speakers as long as there is enough context. But I'm not sure if it's a good idea to list a gazillion of different meanings and usages for the two basic words to learn when it's あく and when it's ひらく...

Maybe it's a really bad idea to look for a general rule or explanation. I'm guessing it's better to focus on one specific case in a particular sentence and context at a time. Or it may be a good idea to just relax and wait until you figure out everything by yourself.

I'm pretty sure I've even read some of those topics before, but it keeps bothering me. Thanks for the help. I suppose it will sink in eventually with time.

All I can think of is the lady's voice in the lift saying "ドアが閉まります" then "ドアが開きます（ひらく）"

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merlin.codex Wrote:ドア／門など　が開く - It can mean "open", of course, but you'll have less trouble remembering it as "unlocked".

That seems a little to imprecise for my taste; ドアが開く means "the door opens" and often has a potential meaning -- intransitive verbs can usually mean "is able to X" and not just X. Someone might ask その窓、開く？ meaning "does it open" or "will it open"; 開かない might not mean "locked" -- it could mean the window is bolted shut, or doesn't even have a mechanism to open it.

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http://nihognodaybydayenglish.blogspot.c...iraku.html

merlin.codex Wrote:There are various uses but most times you can easily distinguish the two by the preceding particle. ひらく is mainly used with を, but there are times when it goes with が, while あく goes only with が.

Well, wasn't it that the OP got confused by them because they can work as intransitive verbs? See how he phrased it:

arch9443 Wrote:But I know I've heard both あく and ひらく when referring to a door.

Probably this means how they can be ドアがあく and ドアがひらく. On top of that, you can say ドアをひらく because ひらく can work as a transitive verb. And they all mean "open" in English, so it's confusing as hell to him. Or so I thought.

Grammar points and differences in nuance like this are related to how potential forms and intransitive verbs etymologically stem from the same place, i.e., 自発, which is not taught in grammar books for foreigners. I remember I talked about this somewhere on this forum in a long series of posts, so if you're interested, you can search my posts, though I don't guarantee its accuracy at all; I don't remember exactly what I wrote.

Anyway, since merlin.codex and yudantaiteki brought up a specific point, I'll give a very simple explanation about difference in nuance between ドアがひらく and ドアがあく. (It's literally impossible to give detailed enough explanations for every possible confusing cases, so let's attack each confusing point one-by-one like this!)

As you can see, they are both used as intransitive verbs, i.e., what opens is the door, and there isn't an explicit doer for these "open" actions. At least it's out of focus in the speaker's mind. Who opens the door? Doesn't matter.

So, both are "The door opens" or in a rare case "A door opens." Since they're intransitive verbs, they can be analyzed as potential or at least kind of potential-ish in meaning in some cases. In other words, they might mean "This door is in the state that you can open it if you want to."

Also, the usual intransitive sense is, of course, you're watching the door open or picturing it's opening in your mind. Both ドアがひらく and ドアがあく can mean this way.

Potential-ish or not, they're both "the/a door opens." So what's the difference?

[Edit] Warning: I revised the following so this post focuses on some specific meanings and usages.

The one of the core meanings of あく (and we only focus on 開く) is that stuff that has been an obstacle, blocking you or covering space gets removed. A window is an example it can open in this kind of sense. Also, if a door is locked, and if you use the key to the door, it opens. The lock opened, and the door opened. These two "open"s about the lock and the door can be of this kind. So ドアがあく and 鍵があく are both ok.

ひらく is also open but a little more like "unfold"-ish like a parachute and umbrella. It can include a sliding movement. A door can be seen to open in this manner. A sliding door is ok too. But since ひらく isn't the blocking-stuff-gets-removed kind, it doesn't usually mean the "The lock opens" kind of "open." A wound can open, and this kind is more ひらく than the あく explained above. So 傷口が開く is more likely 傷口がひらく, especially when you're talking about how it gets wider. When a flower blooms, we can say it opens. This open is most of the time ひらく, not あく. So it's 花が開く is 花がひらく. If a gap between two objects gets larger and larger, it's unfold-ish/slide open-ish in a sense rather than something being removed (at least in a native speaker's mind), so you tend to say 差がひらく. This can be a figurative gap too. For example, if you and your rival are competing, and if your score gets worse and worse while your opponent scores more and more points, then 二人の差はどんどん開いていく (ひらいていく).

Most of the cases covered in this post are very confusing ones in that using one verb or the other may not make huge difference in meaning or nuance. So, for example, when a door opens, it can be either the あく kind or ひらく kind depending on how you see it. If you see the open action as blocking stuff getting removed, it's あく, but the door's unfolding movement is in mind, it should be ひらく. Either way, it means "the door opens." 窓が開く is also like that.

花が開く tends to be ひらく, especially when it's the usual "blooming" sense. But if it suddenly pops open as if it unlocked something that has prevented it from opening, either will work. Onomatopoeic words such as ぱっと and ぽんと make it easier to take あく in this case. 目が開く is harder to determine if it's ひらく or あく unless you know how the speaker is picturing it in his mind. He might be seeing it as an unfolding/sliding way. But it can be like the eyelid (which prevents you from seeing the eye) goes away, which means あく.

An important case of ひらく which the "unfolding/sliding" image may not be able to explain is the "open up your heart" kind of "open." 彼女の心が開く means she becomes open to you and now tries to understand you as well. This is ひらく. Also, for example, as I said earlier, 鍵 usually collocates with あく. But it can be figurative like the door to another person's mind getting unlocked (e.g., 心の鍵が開く). In this case, ひらく may work better.

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if it's 目を見開く then it's mihiraku but anyways...... for me i just learn the differences through fun immersion.

Thank you, magamo, that is a really great explanation. It may not explain -everything- about these difficult words, but it really clarified a lot in my mind.