These words refer to the highest point of something. Summit and peak both refer most concretely to mountains; peak , however, can indicate the whole mountain or its upper part whereas summit is specifically restricted in reference to the topmost surface alone: climbing the peak to reach the summit. In metaphorical use, this distinction is lost, both words referring to the position of greatest importance, intensity or power. Summit is the more formal of the two and has come to refer specifically to high-level conferences, as between heads of state: the settling of nuclear policy at the summit . Peak suggests that point or moment at which something is most typical or at its best: when the Roaring Twenties were at their peak ; a book produced when he was at the peak of his powers. Summit is less often used in this metaphorical way.

Pinnacle can refer to a turret or, more commonly, to a peak or its summit , but it may sometimes suggest a leaner, taller silhouette than peak . Used metaphorically, it functions as a hyperbolic substitute for peak , often in stock combinations that approach the cliché: the pinnacle of success. Acme can theoretically refer to a summit but is now used almost exclusively in a metaphorical way to refer to the quintessence of some abstract quality. It appears also in stock combinations: the acme of perfection. Apex refers to the vertex of an angle, but can indicate also the tip or top of something, or something at its maximum or its turning point: a battle that reached its apex the next afternoon. All three words can become empty metaphors, especially when used indiscriminately because of their imagined status or elegance.

Neither zenith nor climax makes any literal reference to a mountain peak or summit . Zenith refers to the celestial point directly overhead. Metaphorically, it suggests anything at its culmination or highest development; as such it is a useful intensification of peak : fearing that the team would reach its peak too early, before the competition had reached its zenith . Also, zenith is more often used or suggest something positive, whereas peak is not so restricted: His mastery of new painting techniques was at its zenith when the taste of his times had reached a peak of vulgarity. Most concretely, climax refers to the turning point of a play or a kind of rhetorical build-up in an oration. Metaphorically, the word is especially pertinent to indicate the point of fullest development in something that grows or has cyclic stages: The emergence of the butterfly from the chrysalis is the climax of its life cycle.