Anatomical landmarks are features on the surface of the tooth which are either elevations or depressions. These landmarks help the tooth in performing their functions and also in their identification. Here we will be discussing the landmarks showing only concavities or depressions. Fossa. Fossa is an irregular depression or concavity on the surface of the crown. They are present on all teeth and are named according to their location. In anterior teeth they are present on the lingual surface and are called lingual fossa. In posterior teeth they are on the occlusal surface and called triangular fossa or central fossa. Lingual fossa is present on the lingual surface of all anterior teeth. Incisors have one lingual fossa, and canines have 2 lingual fossae. No grooves or pits are present in lingual fossa. Except in maxillary lateral incisor which may have grooves and a pit.Triangular fossa are present on the occlusal surface of all premolars and molars. They are triangular in shape with their base towards the marginal ridge and apex towards the center. They are always 2 in number. One mesial triangular fossa and one distal triangular fossa. They have pits and grooves present in them. Central fossa are found on the occlusal surface of all molars. Each molar has 1 central fossa which has a pit and grooves present in them. Sulcus. A sulcus is a linear concavity or depression on the crown. They are present in the posterior teeth on their occlusal surface. They have a developmental groove at their base. For example in maxillary 1st premolar the central sulcus which runs mesiodistally. Groove. A developmental groove is a sharply defined groove or line on the tooth surface. They are present in posterior teeth and absent in anterior teeth. Except in maxillary lateral incisor which may have grooves on the lingual surface. They are named according to their location. They may be present on any surface of the crown. On occlusal surface they are present at the bottom of a sulcus or fossa. Like the central groove in maxillary premolars, in maxillary molars and mandibular molars. Whereas, on other surfaces they may not be present in any prominent depression. Like mesial marginal groove in maxillary 1st premolar, mesio-bucccal groove and distobuccal groove in mandibular 1st molar. Apart from the developmental grooves which have specific names, many teeth show supplemental grooves. Like in maxillary 2nd premolar or mandibular 1st molar. These grooves are not individually given names and are just collectively called supplemental grooves. This is because there presence is not same for everyone in a population. For example everyone has one central groove in maxillary 2nd premolar. But the number and position of supplemental grooves may vary person to person. Some may have few some may have many. Pit. A pit is a pinpoint depression on the surface of the crown. It is located at the junction of two or more grooves or at the terminus of a groove. They are seen in all posterior teeth and absent in anterior teeth. Except for maxillary lateral incisor where in the lingual fossa a lingual pit may be present. They are named according to their location. Like, all premolars and molars have a mesial pit and a distal pit. And all molars have a central pit. All pits on the occlusal surface are present in a fossa. Whereas on other surfaces pits may not be present in any prominent depression. Like in mandibular molar, Buccal pit on the buccal surface located at the terminus of mesiobuccal groove and lingual pit on lingual surface located at the terminus of lingual developmental groove.