Answer:
Secular nation
Step-by-step explanation:
The principle that state should be separate from the religious institutions is called secularism and the state that followed the concept of secularism is called secular state.
Secular states are neutral in matters of religion, it doesn't support irreligion or religion. It also treats all its citizens equally and avoids preferential treatment to citizens based on religion. Such states doesn't have any religion but absence of state religion doesn't mean that it is secular. USA a secular state as it doesn't have any state religion and its government doesn't interferes in religious matters.