若是 (ruò shì): if

If it doesn't rain tomorrow, we'll go hiking; if it rains, we'll go to the museum instead.

If you had told me earlier, I could have helped you solve this problem.

If it weren't for your support, I might have given up long ago.

If you want to take part in this competition, you'll have to start preparing seriously from now on.

If there's a traffic jam, we might be late, so it's best to set off half an hour early.