Deep frying differs from pan frying by employing enough oil to immerse the food altogether. As a technique, it resembles boiling more than pan frying, with the essential difference that the oil is heated far above the boiling point of water, and so will dehydrate the food surface and brown it.
From the book On Food and Cooking (2nd edition) by Harold McGee. © 2004 Harold McGee.
By permission of Scribner, a division of Simon & Schuster, Inc.