The word erudition came into Middle English from Latin. A scholar is erudite (Latin eruditus) when instruction and reading followed by digestion and contemplation have effaced all rudeness (e- (ex-) + rudis), that is to say smoothed away all raw, untrained incivility. Common usage has blurred the distinction from "learned".
Erudition is the depth, polish and breadth that is applied to education from further readings and understanding of literary works. The Latin word educare means to bring up or train; hence an educated person has come to think critically and logically. An erudite person has both deep and broad familiarity with a certain subject, often gained through study and extensive reading of the subject's literature rather than formal scholarship.
For example, a jurist is learned, and knows the law intimately and thoroughly. Thus, an erudite jurist has both deep, specific knowledge of the law, and broad knowledge in the form of social and historical context of law; an erudite jurist may additionally know the laws of other cultures. Erudition in a literary work incorporates knowledge and insights spanning many different fields. When such universal scholars are also at the forefront of several fields, they are sometimes called polyhistors, or polymaths (though the two can mean different things. See either article for further discussion).
The Italian poet Giacomo Leopardi was erudite: he read and studied the classics and was deeply influenced by many philosophers. Other erudite writers include the Roman Marcus Terentius Varro, the English essayist Sir Thomas Browne and the French essayist Michel de Montaigne.