Molars are the rearmost and most complicated kind of tooth

Tooth

Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...

 in most mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s. In many mammals they grind food; hence the Latin name mola, "millstone

Millstone

Millstones or mill stones are used in windmills and watermills, including tide mills, for grinding wheat or other grains.The type of stone most suitable for making millstones is a siliceous rock called burrstone , an open-textured, porous but tough, fine-grained sandstone, or a silicified,...

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Adult humans have twelve molars, in four groups of three at the back of the mouth. The third, rearmost molar in each group is called a wisdom tooth

Third molar

A wisdom tooth, in humans, is any of the usually four third molars. Wisdom teeth usually appear between the ages of 17 and 25. Most adults have four wisdom teeth, but it is possible to have fewer , or more, in which case they are called supernumerary teeth...

. It is the last tooth to appear, breaking through the surface of the gum at about the age of twenty, although this varies from individual to individual.