A label is a piece of paper, polymer, cloth, metal, or other material affixed to a container or article, on which is printed a legend, information concerning the product, addresses, etc. A label may also be printed directly on the container or article. Labels have many uses: product identification, name tags, advertising, warnings, and other communication. Special types of labels called digital labels (printed through a digital printing) can also have special constructions such as RFID tags, security printing, and sandwich process labels. Lithography (from Greek ????? - lithos, "stone" + ???f? - graph?, "to write") is a method for printing using a stone (Lithographic Limestone) or a metal plate with a completely smooth surface. Lithography uses oil or fat and gum arabic to divide the smooth surface into hydrophobic regions which accept the ink, and hydrophilic regions which reject it and thus become the background. By contrast, in intaglio printing a plate is engraved, etched or stippled to make cavities to contain the printing ink, and in woodblock printing and letterpress ink is applied to the raised surfaces of letters or images. The proverb "An apple a day keeps the doctor away," addressing the health effects of the fruit, dates from 19th century Wales. A vegetable is an edible plant or part of a plant other than a sweet fruit or seed. The word is not scientific, however, but instead is largely based on culinary and cultural tradition. Thus the application of the word is somewhat arbitrary and subjective. For example, some people consider mushrooms to be vegetables while others consider them a separate food category. Some vegetables can be consumed raw, and some may (or must) be cooked in various ways, most often in non-sweet (savory or salty) dishes. However, some vegetables are often used in desserts and other sweet dishes, such as pumpkin pies and carrot cakes.