The premolar teeth or bicuspids are transitional teeth located between the canine

Canine tooth

In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...

 and molar

Molar (tooth)

Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....

 teeth. In humans, there are two premolars per quadrant

Circular sector

A circular sector or circle sector, is the portion of a disk enclosed by two radii and an arc, where the smaller area is known as the minor sector and the larger being the major sector. In the diagram, θ is the central angle in radians, r the radius of the circle, and L is the arc length of the...

, making eight premolars total in the mouth. They have at least two cusps

Cusp (dentistry)

A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...

. Premolars can be considered as a 'transitional tooth' during chewing, or mastication

Mastication

Mastication or chewing is the process by which food is crushed and ground by teeth. It is the first step of digestion and it increases the surface area of foods to allow more efficient break down by enzymes. During the mastication process, the food is positioned between the teeth for grinding by...

. It has properties of both the anterior canines and posterior molars, and so food can be transferred from the canines to the premolars and finally to the molars for grinding, instead of directly from the canines to the molars.

The premolars in humans are the maxillary first premolar

Maxillary first premolar

The maxillary first premolar is one of two teeth located in the upper jaw, laterally from both the maxillary canines of the mouth but mesial from both maxillary second premolars...

, maxillary second premolar

Maxillary second premolar

The maxillary second premolar is one of two teeth located in the upper jaw, laterally from both the maxillary first premolars of the mouth but mesial from both maxillary first molars...

, mandibular first premolar

Mandibular first premolar

The mandibular first premolar is the tooth located laterally from both the mandibular canines of the mouth but mesial from both mandibular second premolars. The function of this premolar is similar to that of canines in regard to tearing being the principal action during mastication, commonly...

, and the mandibular second premolar

Mandibular second premolar

The mandibular second premolar is the tooth located distally from both the mandibular first premolars of the mouth but mesial from both mandibular first molars. The function of this premolar is assist the mandibular first molar during mastication, commonly known as chewing. Mandibular second...

.

There is always one large buccal

Cheek

Cheeks constitute the area of the face below the eyes and between the nose and the left or right ear. They may also be referred to as jowls. "Buccal" means relating to the cheek. In humans, the region is innervated by the buccal nerve...

 cusp, especially so in the mandibular first premolar. The lower second premolar almost always presents with two lingual

Tongue

The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

 cusps.

Molar teeth by definition are permanent teeth distal to the canine

Canine tooth

In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...

s, preceded by deciduous

Deciduous teeth

Deciduous teeth, otherwise known as reborner teeth, baby teeth, temporary teeth and primary teeth, are the first set of teeth in the growth development of humans and many other mammals. In some Asian countries they are referred to as fall teeth as they will eventually fall out, while in almost all...

 premolars.
In primitive placental mammal

Eutheria

Eutheria is a group of mammals consisting of placental mammals plus all extinct mammals that are more closely related to living placentals than to living marsupials . They are distinguished from noneutherians by various features of the feet, ankles, jaws and teeth...

s there are four premolars per quadrant. The most mesial two have been lost in Catarrhines (Old World monkeys and apes, including humans

Homo (genus)

Homo is the genus that includes modern humans and species closely related to them. The genus is estimated to be about 2.3 to 2.4 million years old, evolving from australopithecine ancestors with the appearance of Homo habilis....

). Paleontologists refer to human premolars as Pm3 and Pm4.