1The mouth — the body part on a person or animal used for eating and speaking.
彼は口を大きく開けてパンを食べた。
He opened his mouth wide and ate the bread.
子どもは口の中に虫歯があって歯医者に行った。
The child had a cavity in his mouth and went to the dentist.
彼女は口に手を当てて驚いた顔をした。
She put her hand over her mouth with a look of surprise.
2An opening, hole, or gap — an orifice or entrance of something.
洞窟の口から冷たい風が吹き出している。
Cold air is blowing out from the mouth (opening) of the cave.
排水溝の口が落ち葉で詰まっている。
The opening of the drainage ditch is clogged with fallen leaves.
3The mouth of a bottle; a spout, nozzle, or mouthpiece of a container or instrument.
ペットボトルの口をしっかり閉めてください。
Please close the mouth of the plastic bottle tightly.
蛇口をひねると、勢いよく水が出てきた。
When I turned the faucet, water came out forcefully.
この急須は注ぎ口が細くて使いやすい。
This teapot has a narrow spout and is easy to use.
4A gate, door, entrance, or exit — used to refer to an access point to a place.
非常口の前に荷物を置かないでください。
Please don't leave luggage in front of the emergency exit.
駅の改札口で待ち合わせよう。
Let's meet at the station's ticket gate.
登山口までバスで行くことができる。
You can take a bus to the trailhead (entrance to the mountain path).
5Speaking, speech, or talking — including gossip or conversing (see phrase 口を利く).
彼は他人の悪口を言うのが好きで、口が軽い。
He likes talking badly about others; he's gossipy.
面接ではあまり口を利かない方が印象がいいこともある。
In interviews, sometimes it's better not to talk too much; it can leave a better impression.
口を開けばすぐに余計なことを言ってしまう。
As soon as he opens his mouth he says unnecessary things.
6Taste or palate — used for whether food suits someone's taste (e.g., 口に合う).
この料理は私の口に合わない。少し辛すぎる。
This dish doesn't suit my taste. It's a bit too spicy.
高級ワインは口当たりがまろやかだ。
The high-quality wine has a mellow mouthfeel.
祖母の作る味噌汁は誰の口にも合う味だ。
My grandmother's miso soup tastes good to everyone.
7The 'mouths to feed' — used to refer to the number of dependents one must support, as in the phrases 口を養う (to feed one's family) or 口を減らす (to reduce the number of mouths to feed).
彼は家族五人の口を養うために、休まず働いている。
He works without rest to feed his family of five.
厳しい時代には、口を減らすために子どもを奉公に出すこともあった。
In hard times, children were sometimes sent out to work as apprentices to reduce the number of mouths to feed.
8A vacancy or available position — an opening for work (e.g., 働き口).
彼は新しい働き口を探している。
He is looking for a new job (position).
大学を出てから働き口が見つかるまで時間がかかった。
After graduating from university, it took time to find a job.
町に新しい働き口ができて若者が戻ってきた。
New job openings appeared in town and young people returned.
9An invitation or summons — used to indicate being invited or called (see 口がかかる).
飲み会の口がかかったので、今夜は参加するつもりだ。
I've been invited to a drinking party, so I plan to go tonight.
仕事の口がかかって、一度面接を受けることになった。
I was offered a job opportunity and will attend an interview.
10A kind, sort, or type — often used in compounds to indicate a style or degree (e.g., 辛口, 甘口).
ワインは辛口の方が好きだ。
I prefer dry (less sweet) wines.
子ども向けの商品は甘口の味付けになっている。
Products for children are seasoned to be mild/sweeter.
11The opening or beginning of something — the trigger or first step (as in 口火を切る).
彼の一言が議論の口火を切り、白熱した討論になった。
His single remark sparked the debate, and it turned into a heated discussion.
会議の口火を切るのは上司の役割だ。
It's the boss's role to kick off the meeting.
12A counter/suffix for mouthfuls or shares and for stove burners — e.g., 一口 (a mouthful), 一口 (an investment share), or コンロの口数.
ケーキを一口だけ食べさせてください。
Let me have just one bite of the cake.
その投資ファンドに一口出資した。
I invested a share in that fund.
キッチンには二口コンロが付いている。
The kitchen has a two-burner stove.
13A counter for swords, blades, etc. — written with 口 but often read ふり in museum or formal contexts (e.g., 一口 read as ひとふり).
展示室には江戸時代の刀が三口（さんふり）並んでいる。
Three Edo-period swords are lined up in the exhibition room.
刀剣展示会で、貴重な太刀が二口紹介された。
At the sword exhibition, two precious swords were introduced.