What is the difference between atheism, secularism, freethought, and humanism?

These four terms are often used interchangeably but refer to distinct concepts:

In more detail:

• Atheism: Simply a lack of belief in God. Says nothing about ethics, politics, or meaning. An atheist can be immoral, apolitical, or anything else atheism addresses only the question of God's existence.
• Secularism: Primarily a political principle. Argues government should operate independently of religious institutions. Does NOT mean anti-religion it protects both religious freedom and freedom from religion. A deeply religious person can fully support secularism.
• Freethought: An intellectual method, not a conclusion. Freethinkers form beliefs through logic, evidence, and reason rejecting dogma and tradition as authoritative sources.
• Humanism: A comprehensive life philosophy. Affirms human dignity, autonomy, and reason. Holds that ethics and meaning can be built without supernatural foundations. Emphasizes compassion, human rights, critical thinking, and democratic society.