Fanatism vs. Fanaticism — What's the Difference?

(archaic) excessive intolerance of opposing views

Fanaticism (from the Latin adverb fānāticē [fren-fānāticus; enthusiastic, ecstatic; raging, fanatical, furious]) is a belief or behavior involving uncritical zeal or an obsessive enthusiasm. Philosopher George Santayana defines fanaticism as "redoubling your effort when you have forgotten your aim".

Fanaticism.

Excessive, irrational zeal, especially in politics or religion.

The characteristic or practice of being a fanatic.

Excessive enthusiasm, unreasoning zeal, or wild and extravagant notions, on any subject, especially religion, politics or ideology; religious frenzy.

Excessive intolerance of opposing views