The raised area on the occlusal surface of molars that functions primarily in grinding food is called a cusp.

Cusps are pointed or rounded projections found on the chewing surfaces of premolars and molars. Their primary role is to help in the mechanical breakdown of food by piercing and grinding it during mastication. This is in contrast to other features on the tooth surface such as:

- Fossa: These are depressions or hollows on the occlusal surface that serve as areas where the cusps of the opposing teeth fit during occlusion.
- Tubercle: These are small, rounded elevations on the surface of a tooth, often found on the crowns of incisors and canines, but they are not primarily involved in grinding.
- Ridge: This is a linear elevation on the surface of a tooth, such as marginal ridges or triangular ridges, but is not the main grinding structure.

Therefore, the term cusp accurately describes the raised areas on molar teeth that are essential for the process of grinding food effectively.

Reference: Wheeler's Dental Anatomy, Physiology and Occlusion, 10th Edition, Chapter 7: Tooth Morphology and Function