The feeling of disappointment when you realize something you believed in isn't as good or true as you thought.
From disillusion (to remove illusion, dis- + illusion) + -ment (noun suffix from Latin -mentum, creating abstract nouns). The word became prominent in English by the 1850s.
Disillusionment became THE defining word of the 20th century—after WWI, it captured what millions felt, and authors like Hemingway and Fitzgerald made it a literary obsession, turning it from a philosophical concept into an emotional trademark of modernity.
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