Some similar words often occur but must be used in different occasions,please take some example
Such as “busy” and “have no time” , the former is used on big shot and the latter used ourselves.

Question

Answer

"I'm busy" or "Sorry, I'm a little busy" is a normal expression used in BOTH formal and informal situations. 
To say "I have no time" is kind of rude, it implies the person you're speaking to is not important enough for your time.

Answer

ok, I just want to know some well-mannered expression.

Answer

This question is a little open-ended.