How to you say a formal "Okay" and an informal "Okay" in Japanese?

Question:

Answer:

Depends on context, but...

Formal: Yes/Okay - Hai. はい。
Understood - Wakarimashita. わかりました。


Informal: There really isn't a specifically 'informal' way of saying 'Okay' in Japanese. I mean, people use informal language because they get lazy, but how do you shorten "Hai"?

I guess informally, you'd nod, give a gesture, or just mumble something that you'd do in English like "uhn", or "uh huh".