開: to open; to start

開 [开] kāi

adjective | verb
: to open; to start; to turn on
: to boil
: to write out (a prescription, check, invoice etc)
: to operate (vehicle)

開く | あく aku

godan verb with ku ending | intransitive verb
: to open (e.g. doors)
: to open (e.g. business)
: to be empty
: to be vacant; to be available; to be free
: to be open (e.g. neckline)
: to have been opened (of one’s eyes, mouth)
: to come to an end
: () to open (one’s eyes, mouth)
: () to have a hole; to form a gap; to have an interval (between events)

開き | ひらき hiraki

noun
: opening; gap
: (Suffix) dried and opened fish

開く | ひらく hiraku

godan verb with ku ending | transitive verb
: to open (e.g. a bank-account, festival)
: () to spread out; to open up (flower bud, umbrella, etc.); to widen (gap, distance, width)
: to hold; to give (party, conference)

開ける | あける akeru

ichidan verb | transitive verb
: to open (a door, etc.); to unwrap (e.g. parcel, package)
: to open (for business)
: to empty; to clear out; to make space; to make room
: () to dawn; to grow light
: to end

開ける | ひらける hirakeru

ichidan verb | transitive verb
: to become opened up; to improve; to get better;
: to develop; to progress; to become civilized (civilised); to be up-to-date;
: to be enlightened; to be sensible

開かる | はだかる hidakaru

godan verb with ru ending | intransitive verb
: (Usually written using kana alone) to be separated; to be exposed; to be wide open
: to stand with one’s limbs apart (blocking the way)

開ける | はだける hidakeru

ichidan verb | transitive verb
:(Usually written using kana alone) to open; to bare; to expose
: to stretch

開[开]口 kai1kou3: to open one’s mouth; to start to talk
[かいこう kaikou: opening; aperture (e.g. camera);
: opening one’s mouth; beginning to speak
: open; broad]

開門[开门]kai1men2: to open the door [開門 | かいもん kaimon: opening the gate]

開車[开车]kai1che1: to drive a car

開夜車[开夜车]kai1 ye4 che1: to work late into the night

開會[开会]kai1hui4: to hold a meeting; to attend a meeting
[開会 | かいかい kaikai: opening of a meeting]

開[开]花 kai1hua1: to bloom; to blossom; to flower; fig. to burst open; to feel happy or elated; new development grows out
[かいか kaika: flowers budding; blooming; flowering
: showing results; becoming popular]

開[开]始 kai1shi3: to begin; beginning; to start; initial
[開始 | かいし kaishi: start; commencement; initiation]

開學[开学] kai1xue2: foundation of a University or College; school opening; the start of a new term
[開学 | かいがく kaigaku: establishment of a university]

開[开]玩笑 kai1 wan2xiao4: to play a joke; to make fun of; to joke

開[开]展 kai1zhan3: (begin to) develop; unfold; to start; to launch; to open; to carry out

展開[开] zhan3kai1: to unfold; to carry out; to be in full swing; to launch
[展開 | てんかい tenkai: development; evolution; unfolding
: expansion; deployment; building up]

開[开]放 kai1fang4: to bloom; to open; to be open (to the public); to open up (to the outside); to be open-minded; unrestrained by convention; unconstrained in one’s sexuality
[開放 | かいほう kaihou: open; throw open; liberalization]

離開[离开] li2kai1: to depart; to leave

公開[开] gong1kai1: public; to publish; to make public
[公開 | こうかい koukai: open to the public; exhibit]

召開[开] zhao4kai1: to convene (a conference or meeting); to convoke; to call together

分開[开] fen1kai1: to separate; to part

Japanese expression
*開け胡麻 | ひらけごま hirake goma
: Open Sesame!

開け扉 | ひらけとびら hirake tobira
: Lucy Heartfilia’s (of Fairy Tail) summon to open her Celestial Spirits’ door

口を開く | くちをひらく kuchi o hiraku
: to open one’s mouth (to talk)

道を開ける | みちをあける michi o akeru
: to make way for; to make room for; to get out of the way
: to pave the way for; to open up opportunity

叩けよ然らば開かれん | たたけよさらばひらかれん tatakeyo saraba hirakaren
: Knock, and it shall be opened unto you

開いた口が塞がらない | あいたくちがふさがらない aita kuchi ga fusa ga ranai
: to be surprising; to be shocking; to be jaw-dropping

Chinese idiom
*芝麻開門 zhi1ma kai1men2: Open Sesame!

開門見山 [开门见山] kai1 men2 jian4 shan1
: lit. to open the door and see the mountain; fig. to get right to the point

見錢眼開 [见钱眼开] jian4 qian2 yan3 kai1
: to open one’s eyes wide at the sight of profit (idiom); thinking of nothing but personal gain; money-grubbing

一把鑰匙開一把鎖 [一把钥匙开一把锁] yi1 ba3 yao4 shi5 kai1 yi1 ba3 suo3
: One key opens one lock. There is a different solution for each problem

凡事總有一個開頭 [凡事总有一个开头] fan2 shi4 zong3 you3 yi1 ge4 kai1 tou2
: Everything starts somewhere

打開天窗說亮話 [打开天窗说亮话] da3 kai1 tian1 chuang1 shuo1 liang4 hua4
: not to mince words; not to beat about the bush

開弓沒有回頭箭 [开弓没有回头箭] kai1 gong1 mei2 you3 hui2 tou2 jian4
: lit. once you’ve shot the arrow, there’s no getting it back; fig. once you started something, there’s no turning back; to have to finish what one started; to be determined to reach one’s goals in spite of setbacks