APEX

UK: /ˈeɪpɛks/ US: /ˈeɪpɛks/ ,(ā′peks)

Inflections of 'apex' (n):

apexes

npl

apices

npl

Collins Concise English Dictionary © HarperCollins Publishers::

APEX / ˈeɪpɛks/ acronym:noun

1. Advance Purchase Excursion: a reduced airline or long-distance rail fare that must be paid a specified number of days in advance
2. (in Britain) Association of Professional, Executive, Clerical, and Computer Staff

WordReference Random House Learner's Dictionary of American English © 2025

a•pex /ˈeɪpɛks/   n. [countable] , pl. a•pex•es, a•pi•ces 

/ˈeɪpəˌsiz, ˈæpə-/.  
1. the highest point;
   summit:
   the apex of a mountain; the apex of a career.
2. the tip or point:
   the apex of the tongue.

WordReference Random House Unabridged Dictionary of American English © 2025

a•pex  (ā′peks), n., pl. a•pex•es, a•pi•ces 

(ā′pə sēz′, ap′ə-). 
1. the tip, point, or vertex;
   summit.
2. climax;
   peak;
   acme:
   His election to the presidency was the apex of his career.
3. [Astron.] See solar apex. 

• Latin
• 1595–1605

APEX  (ā′peks), 

1. a type of international air fare offering reduced rates for extended stays that are booked in advance. [1970–75;
   A(dvance) P(urchase) Ex(cursion)]

Collins Concise English Dictionary © HarperCollins Publishers::

apex / ˈeɪpɛks/ noun (apexes, apices / ˈæpɪˌsiːz ˈeɪ-/)

1. the highest point; vertex
2. the pointed end or tip of something
3. a pinnacle or high point, as of a career, etc

Etymology: 17th Century: from Latin: point