Logos

Logos ( /ˈloʊɡɒs/, /ˈlɒɡɒs/, or /ˈloʊɡoʊs/; Greek: λόγος, from λέγω lego "I say") is an important term in philosophy, psychology, rhetoric, and religion. Originally a word meaning "a ground", "a plea", "an opinion", "an expectation", "word," "speech," "account," "reason," it became a technical term in philosophy, beginning with Heraclitus (ca. 535–475 BC), who used the term for a principle of order and knowledge.