I've just started learning Japanese last week.
I'm playing a video game in Japanese. One of the characters said: "礼を言う" (rewoiu) just by itself. The English translation was "Thank you."
I didn't recognize this as any version of "thank you" I had heard before.
The translation I get when searching is: "Say thanks". But this is basically just a non-past verb. Can you use non-past verbs by themselves usually?
Does "say thanks" in Japanese also mean "thank you"? If so, when is it appropriate to use this over other common forms of thank you; what's the difference between this and "arigatou"?