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" but the two terms are quite different.
Erudition is the depth, polish and breadth that education confers. The Latin word educāre means to bring out or train; hence an educated person has come to think critically and logically. An erudite person has both deep and broad familiarity with general subjects and is usually knowledgeable in a particular subject, by virtue of study and extensive reading of the subject's literature.
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.
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.
In Latin, eruditus means enlightened, or cultivated. Enlightenment comes from understanding and not just from learning.