開く · godan verb (-ku)
| Form | Positive | Negative |
|---|---|---|
| Dictionary | 開く | 開かない |
| Polite | 開きます | 開きません |
| Past polite | 開きました | 開きませんでした |
| Past | 開いた | 開かなかった |
| Te-form | 開いて | 開かないで |
| Desire | 開きたい | 開きたくない |
| Potential | 開ける | 開けない |
| Passive | 開かれる | 開かれない |
| Causative | 開かせる | 開かせない |
| Causative passive | 開かせられるalso 開かされる | 開かせられないalso 開かされない |
| Volitional | 開こう | |
| Polite volitional | 開きましょう | |
| Imperative | 開け | 開くな |
| Conditional | 開けば | 開かなければ |
| Tara conditional | 開いたら | 開かなかったら |
godan verb (-ku), intransitive verb
open; come open
Only when written 開く
Intransitive: a door, window, lid, or similar object opens by itself or is in an openable/opened state. The person who opens it is normally expressed with 開ける, not this verb.
The door opened in the wind.
godan verb (-ku), intransitive verb
open for business; start operating
Only when written 開く
Used when a shop, office, facility, or service opens at a certain time or begins business.
This shop opens at nine in the morning.
godan verb (-ku), intransitive verb
be empty; be vacant; be available; be free
Only when written 空く
Used with physical spaces such as seats and rooms, and also with a person's time or schedule. 空く is the usual kanji for this sense.
Please let me know when a seat becomes available.
Are you free tomorrow afternoon?
godan verb (-ku), intransitive verb
be open; be low-cut; leave an opening
Only when written 明く
Used for openings in clothing or around the body, such as a neckline, collar, or chest area being open or cut low. Associated with this with 明く, but kana spelling is also a safe modern choice.
This shirt is too open around the neck.
godan verb (-ku), intransitive verb
be open; come open
Only when written 明く
Intransitive use for the eyes, mouth, and similar body parts being open or having opened. In ordinary modern Japanese, kana or 開く may be seen, while lists 明く.
I was so surprised that my mouth stayed open.
godan verb (-ku), transitive verb
open one's eyes or mouth
Only when written 明く
Transitive use with body parts such as eyes or mouth. This is limited and old-fashioned in modern Japanese; 開ける is the normal everyday verb for actively opening one's eyes or mouth.
In old writing, 口を明く is close to the modern expression 口を開ける, meaning to open one's mouth.
godan verb (-ku), intransitive verb
Only when written 明く
Limited use for a period or state ending. It is especially associated with 明く and is often safest to learn through fixed expressions rather than as a freely productive modern verb.
喪が明く is an expression meaning that the period of mourning comes to an end.
godan verb (-ku), intransitive verb
have a hole; form a gap; have an interval
Only when written 開く / 空く
Used when a hole appears, a gap opens up, or time is left between events. 開く is common for holes; 空く is common for empty space or time intervals.
See also: 穴が開く
A hole opened in my sock.
There is a one-hour gap before the next appointment.
That restaurant opens at 5 p.m.
A seat opened up on the train, so I sat down.
That dress has a low, open neckline.
The baby's eyes finally opened.
空く describes a space becoming empty or vacant, the opposite of 埋まる describing a space becoming filled or crowded.
開く means a shop or facility opens, the opposite of 引ける, which means it closes or lets out for the day.
開く written as あく is limited to things like doors, shops, and gaps opening by themselves, while the same kanji read ひらく is a broader verb that also covers unfolding, holding events, and deliberate transitive action.
空く (あく) means a space becomes completely empty or a position becomes vacant, while 空く (すく) emphasizes a reduction in crowding or density; they share the same kanji but differ in reading and nuance.
Attested spelling for body openings and for a period coming to an end, but it is less common in ordinary modern writing than kana or other spellings in many contexts.