• 質問しつもん — question
• 問題もんだい — problem, issue
• 訪問ほうもん — visit
• 問屋とんや — wholesale store
• 問答もんどう — dialogue, Q&A
• 問とい合あわせ — inquiry

The character 問 is composed of the radical 門もん (gate) and the component 口くち (mouth). It symbolizes someone speaking through a gate — representing inquiry, questioning, or requesting information from the other side.

質問しつもんがあれば、どうぞ。
If you have any questions, please ask.

問題もんだいを 解といてください。
Please solve the problem.