問 (Kanji for question, problem)

Onyomi

MON

The MONK, standing at the temple gate, asks you a question : (a Zen koan) with his mouth. If you answer wrong, you can't get in.

と*う	to ask (BOOBOO: only used in a formal situation, where the wrong answer spells trouble: - the police questioned the suspect, the situation calls his authority into question) F ★★☆☆☆

質問(しつもん) する

question ★★★★★
質 (quality) + 問 (question, problem) = 質問 (question)

a question - usually used in a structured setting: interview, trial, test.　

BOOBOO: in casual conversation, people will say 尋ねる　or 聞く instead of 質問.

問題(もんだい)

problem ★★★★★
問 (question, problem) + 題 (topic) = 問題 (problem)

problem - as in "environmental pollution", also as in "homework problem"

疑問(ぎもん)

a doubt　 ★★★☆☆
疑 (doubt) + 問 (question, problem) = 疑問 (a doubt　)

a doubt　（疑問がある＝ I have doubts about it.)

Gate has NOTHING IN THE CENTER, IT'S OPEN - so you can walk through it.

There is an interval of one DAY between things, and you ask a question with your MOUTH.