Examples of using "本当だよ!" in a sentence and their english translations:
Really!
I swear on my life that it's true!
In a way, what your friend has said is true.
I swear on my life that it's true!
- "It's true," said John.
- "That's true," said John.
I saw a UFO! I'm serious! Please, believe me. I'm not crazy or anything like that.