(, , or ;
Greek: , from λέγω
lego "I say") is an important term in western
philosophy,
psychology,
rhetoric, and
religion. It is a Greek word meaning "a ground", "a plea", "an opinion", "an expectation", "word", "speech", "account", "to reason", but 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.