Mug

Mug
A mug is a sturdily built type of cup often used for drinking hot beverages, such as coffee, tea, or hot chocolate. Mugs, by definition, have handles and often hold a larger amount of fluid than other types of cups. In more formal settings a mug is usually not used for serving hot beverages, with a teacup or coffee cup being preferred.

Many mugs are made of ceramic materials such as earthenware, bone china, porcelain or stoneware. Some are made from strengthened glass, such as Pyrex. Other materials, including plastic, steel and enameled metal are used where break resistance is at a premium, such as for campers. Techniques such as silk screen printing or decals can be used to apply decorations; these are fired onto the mug to ensure permanence.

Functions
Though at first glance a very simple object, the mug serves a number of functions which make it especially suited to holding hot liquids:
Provides a handle: (i) for grasping, and (ii) provides a cool area of the mug that is insulated from the hot liquid by distance.
Hot beverages may be too hot to drink, with temperatures often nearing the boiling point of water. The thick walls of a typical mug will absorb much of this heat when the liquid is first poured into the mug and so lower the beverage closer to potable temperatures.
The mug stores some heat from the beverage, and so prevents it from cooling too quickly. The design of a mug helps insulation: (i) thick walls separate the beverage from the cool external air, and (ii) an indented base separates the beverage from the surface upon which the mug is set. The shape of the base forms the characteristic O-shaped stain, so often seen upon desks and documents.