n. pl. a·pex·es or a·pi·ces (āpĭ-sēz′, ăpĭ-)
a. The highest point of a structure, object, or geometric figure: the apex of a hill; the apex of a triangle.
b. The usually pointed end of an object; the tip: the apex of a leaf.
a. The highest level or degree that is attained, as in a hierarchy. See Synonyms at summit.
b. The period of greatest achievement: won several Olympic medals at the apex of her career.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.