2. A principle that relations and dealings between the government and the governed should be guided by fairly-established rules, procedures, and policies that assure fundamental fairness to all who are subject to the government's authority.
3. As applied to a legal proceeding like a criminal or civil trial, a requirement that the proceeding be conducted according to fair and open rules and procedures that adequately safeguard individual rights and liberties. Sometimes also called "procedural due process."
4. A judicially-created doctrine recognizing that certain fundamental rights, being essential to freedom and the ability of individuals to define themselves and their relationships to others, can't be denied or impaired by the government absent the most compelling justification. Sometimes also called "substantive due process."