A sentence-ending phrase expressing the speaker's hope or wish in a softened way (e.g., "I hope..." or "It would be nice if..."). Often used at the end of a sentence.
明日雨が降らないといいのだが。
I hope it doesn't rain tomorrow.
彼が合格してくれるといいのだが、結果はまだわからない。
I hope he passes, but the results are not known yet.
もっと時間があれば、といいのだが。
I wish I had more time.
この薬が効くといいのだが、副作用が心配だ。
I hope this medicine works, but I'm worried about side effects.