How can you say best thing in the one word?

It's impossible to say the "best thing" in one word because "best" is subjective and depends on the context.

Here's why:

* Best for whom? What is best for one person might not be best for another.

* Best in what way? Are we talking about the best food, the best movie, the best idea?

Instead of trying to find a single word, it's more accurate to specify what you're referring to. For example, you could say:

* "Amazing" (if you're talking about something that's impressive)

* "Perfect" (if you're talking about something that's ideal)

* "Wonderful" (if you're talking about something that brings joy)

Ultimately, the best word depends on the specific situation.