1A name suffix attached to males of equal or lower status — boys, classmates, junior colleagues. Common in schools, workplaces, and among friends. More familiar than -san, but more neutral and less cute than -chan.
田中くん、ちょっとこっち来て。
Tanaka-kun, come over here for a sec.
山田くんはクラスで一番背が高い。
Yamada-kun is the tallest in our class.
新入社員の佐藤くんに資料の準備を頼んだ。
I asked Sato-kun, our new hire, to prepare the materials.
幼なじみの健くんとは今でも仲がいい。
I'm still close with Ken-kun, my childhood friend.
2A suffix occasionally used by men to address junior female colleagues. Seen in formal/workplace settings, but in modern usage it can come across as patronizing or sexist, so it should be used with care.
昔の上司は女性社員も『〜くん』と呼んでいた。
My old boss used to call female employees with '-kun' too.
3An archaic honorific suffix (roughly "sir" / "madam"). Survives today mainly in the Japanese Diet, where the chair addresses members of either gender as "~kun" when calling on them to speak.
議長が「鈴木君、答弁をお願いします」と発言を求めた。
The chair called on the member, saying, 「Suzuki-kun, please give your response.」