To Inquire
transitive verb, ichidan verb
Remember how 問う means "to question something" and 合わせる means "to join together"? If you're joining your questions together, you're probably trying to to inquire about something. Inquiring is much more involved than plain old asking, after all.
問い合わせる is a phrase you can use when contacting a business or government office to request information or resolve an issue. It's a bit formal, but in an everyday business-speak kind of way, and it doesn't have the philosophical or weighty tone that 問う does.
You probably know how to read 問う and 合わせる already. 問う is still pretty new though, so here's a mnemonic to help you remember the 問 part:
You love to inquire with your toes (と). Whenever you fill out one of those online forms to contact customer support with an inquiry, you do all your typing with your toes. They don't know you're making this inquiry with your toes — but you do, and it makes you chuckle.
メーカーに問い合わせるよ。
I'll contact the manufacturer.
メールで問い合わせてみたら？
Why don't you try sending an inquiry by email?
事前に問い合わせたかったんだけど、電話がつながらなかったんだよね。
I wanted to inquire in advance, but I couldn't get through on the phone.