The summit of a mountain is the highest point of elevation, which is a point on a surface that is higher in elevation than all points immediately adjacent to it. The terms acme, apex, peak (mountain peak), and zenith are synonymous with summit. The term "mountain top" is generally used only for a mountain peak that is located at some distance from the nearest point of higher elevation. A big, massive rock next to the main summit of a mountain is not considered a summit. Whether a highest point is classified as a summit, a subpeak, or a separate mountain is subjective. The International Climbing and Mountaineering Federations definition of a peak is that it has a prominence of 30 meters (98 ft) or more; it is a mountain summit if it has a prominence of at least 300 meters (980 ft) .