What is the different between must and have to?

What is the different between must and have to?

Have to mainly expresses general obligations, while must is used for specific obligations: I have to brush my teeth twice a day. Important: To express obligation, duty or necessity in the future or the past, must and need are not used.

Should and have to difference?

The RFC defines the following words/phrases: "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL". "Have to" implies the necessity behind the requirement of doing a particular task. ''Should'' finds usage to refer to an ethical responsibility.