If you’ve reached the vertex of something, you know it’s all downhill after that, because vertex refers to the highest point on an object, such as the top of a mountain.

In its early usage vertex referred to the top of a person’s head. That meaning is still common, especially in the field of anatomy, but these days you can use the word in a broader sense to refer to the highest point of anything. Still, it’ll help you remember the meaning of vertex if you visualize the top of someone’s head — the highest point — when you think of this word. If you want to get technical, in the field of mathematics, vertex can refer to the point at which lines meet and form an angle, or to the point on a figure, such as a triangle or cone, that is opposite to its base.

Definitions of vertex
  1. noun
    the highest point (of something)
    synonyms: acme, apex, peak, zenith
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    the part of a hat (the vertex) that covers the crown of the head
    roof peak
    the highest point of a roof
    type of:
    extreme, extreme point, extremum
    the point located farthest from the middle of something
  2. noun
    the point of intersection of lines or the point opposite the base of a figure
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    type of:
    intersection, intersection point, point of intersection
    a point where lines intersect
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