1To open something closed — a door, window, box, package — or to unlock it. A transitive verb, written 開ける; the intransitive counterpart is 開く (あく).
暑いので、窓を開けてもいいですか。
It's hot, so may I open the window?
プレゼントの箱を開けると、中に腕時計が入っていた。
When I opened the present box, there was a wristwatch inside.
鍵を開けて、久しぶりに実家のドアを開けた。
I unlocked it and opened the door of my family home for the first time in a while.
缶のふたが固くて、なかなか開けられない。
The can's lid is stiff and I can hardly get it open.
2To open a shop or business for the day; to start operations. Written 開ける.
この喫茶店は朝七時に開けます。
This coffee shop opens at seven in the morning.
父は週末だけ小さな工房を開けている。
My father opens his small workshop only on weekends.
3To empty or clear something out; to make space or room by removing things. Usually written 空ける.
机の上を空けて、書類を広げた。
I cleared the desk and spread out the documents.
すみません、奥の席を空けていただけますか。
Excuse me, could you make room at the seats in the back?
古い荷物を処分して、押し入れを空けた。
I got rid of old stuff and emptied the closet.
4To vacate or clear out a place one has been using (e.g. a room); to move out. Usually written 空ける.
来月までに今のアパートを空けなければならない。
I have to vacate my current apartment by next month.
改装のため、店舗を一度すべて空けることになった。
For the renovation, we have to clear out the whole store once.
5To be away from home or work for a time; to leave one's place temporarily. Usually written 空ける.
出張で一週間、家を空けることになった。
I'll be away from home for a week on a business trip.
長く店を空けると、常連のお客さんが離れてしまう。
If you leave the shop unattended for long, your regular customers drift away.
6To dawn; for night to end and the sky to grow light. An intransitive verb, usually written 明ける.
夜が明けると、鳥が一斉に鳴き始めた。
When day broke, the birds all began to sing at once.
東の空が白々と明けてきた。
The eastern sky was growing pale with dawn.
夜が明けないうちに山を下りよう。
Let's head down the mountain before dawn.
7For a set period to end — the rainy season, a holiday, a mourning period, etc. An intransitive verb, usually written 明ける.
梅雨が明けて、本格的な夏がやってきた。
The rainy season ended and real summer arrived.
連休が明けると、また忙しい毎日が始まる。
Once the long holiday ends, the busy days start again.
8For the new year to begin. Usually written 明ける (famous from the New Year greeting 明けましておめでとう).
年が明けたら、新しいことに挑戦しようと思う。
Once the new year begins, I plan to try something new.
「明けましておめでとうございます」と新年の挨拶をした。
I gave the New Year greeting, "Happy New Year."
9To keep a date or time free; to set time aside, as in 予定を空ける / 時間を空ける. Usually written 空ける.
大事な打ち合わせのために、午後の予定を空けておいた。
I kept my afternoon free for the important meeting.
その日は時間を空けておくので、ぜひ来てください。
I'll keep that day free, so please do come.
10To make a hole in something; to bore or punch an opening, as in 穴を開ける.
ベルトがゆるいので、新しい穴を開けた。
The belt was loose, so I made a new hole in it.
棚を取り付けるため、ドリルで壁に穴を開けた。
I drilled a hole in the wall to put up a shelf.