• Basic forms
• 問う — to ask / to inquire / to question / base form
• 問います — (I) ask / inquire / masu form
• 問うた — asked / inquired / ta form
• 問うて — ask (and…) / te form
• 問わない — do not ask / negative
• 問えば — if (you) ask / conditional
• 問え — ask! / imperative
• Other common forms
• 責任を問う — to hold someone responsible
• 安全性を問う — to question safety
• More
• 問いたい — want to ask / want to
• 問える — can ask / potential
• 問えない — cannot ask / negative potential
• 問っている — is asking / progressive
• 問わなかった — didn’t ask / negative past

問う（とう） is a godan verb with special conjugation patterns (問わ → 問う / 問います / 問うた). Often used in formal or written contexts.