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.
寒くて口が凍えそうだ。
It's so cold my mouth feels like it's freezing.
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.
パイプの口に詰まりがあるようだ。
It seems there's a blockage at the opening of the pipe.
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.
スピーカーの口にホコリが入らないようにカバーをした。
I covered the speaker's opening so dust wouldn't get in.
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.
山道の口で集合してください。
Please meet at the entrance of the mountain trail.
城の口は普段は閉まっている。
The castle gate is usually closed.
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.
7A count of mouths to feed — used to indicate the number of people in a household (e.g., 一家五口).
うちは五口の家族で、食費がかなりかかる。
We're a family of five, so food expenses are considerable.
この家には三口が住んでいる。
Three mouths live in this house (i.e., three people live here).
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).
彼の一言が口を開けて、議論がヒートアップした。
His single remark opened the floor and the debate heated up.
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（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. — often read ふり in museum or formal contexts (e.g., 一振り).
展示室には江戸時代の刀が三振（さんふり）並んでいる。
Three Edo-period swords are lined up in the exhibition room.
侍は一振りの刀を携えて戦った。
A samurai fought carrying a single sword.