Definition: The first amendment to the United States Constitution guarantees the freedom of speech, press, religion, and assembly. It enshrines the idea that citizens are not compelled by law to speak a particular language or hold a certain religious belief. A definition: First Amendment: The First Amendment of the United States Constitution provides for freedom of thought, conscience, and religion. This includes the right to freely express one's political views without fear of persecution. It also protects the free press from arbitrary interference with its operation and the free exercise of religion by individuals or organizations.