Armistice: A temporary agreement between warring parties to cease hostilities. The armistice signed on November 11, 1918 effectively ended World War I.
Big Four: Refers to the four major Allied leaders who negotiated the Treaty of Versailles at the Paris Peace Conference in 1919 - Woodrow Wilson (US), David Lloyd George (UK), Georges Clemenceau (France), Vittorio Orlando (Italy).
National self-interest: The pursuit of goals and benefits that are advantageous for one's own country. This concept clashed with Wilson's idealistic vision of promoting international cooperation.