APEX
apex, solar apex, apex of the sun's way
(noun) the point on the celestial sphere toward which the sun and solar system appear to be moving relative to the fixed stars
vertex, peak, apex, acme
(noun) the highest point (of something); “at the peak of the pyramid”
Source: WordNet® 3.1
Etymology 1
Noun
APEX
(aviation) Acronym of advance purchase excursion (an air fare)
Etymology 2
Proper noun
APEX
(British, trade union) Acronym of Association of Professional, Executive, Clerical and Computer Staff.
Etymology
Noun
apex (plural apices or apexes)
conical priest cap
The highest or the greatest point of something.
(figuratively) The moment of greatest success, expansion, etc.
(geometry) The topmost vertex of a cone or pyramid (in their conventional orientation).
(chiefly, anatomy) The "pointed" fine end of something.
The lowest part of the human heart.
The deepest part of a tooth's root.
(botany) The end of a leaf, petal or similar organ opposed to the end where it is attached to its support; the tip.
(astronomy) The point on the celestial sphere toward which the sun appears to move relative to nearby stars.
(physics) The lowest point on a pendant drop of a liquid.
(mining, US) The end or edge of a vein nearest the surface.
(typography) A diacritic in Classical Latin that resembles and gave rise to the acute.
(typography) A diacritic in Middle Vietnamese that indicates /ŋ͡m/.
(typography) A sharp upward point formed by two strokes that meet at an acute angle, as in "W", uppercase "A", and closed-top "4", or by a tapered stroke, as in lowercase "t".
(attributive, ecology) The top of the food chain
Synonyms
• (highest point): peak, top, summit
• (moment of greatest success, expansion, etc): acme, culmination, height, peak, pinnacle
• (pointed end): end, tip
• See also apex
Coordinate terms
• (sharp upward point): vertex
Source: Wiktionary
A"pex, n.; pl. E. Apexes; L. Apices. Etym: [L.]
1. The tip, top, point, or angular summit of anything; as, the apex
of a mountain, spire, or cone; the apex, or tip, of a leaf.
2. (Mining)
Definition: The end or edge of a vein nearest the surface. [U.S.] Apex of
the earth's motion (Astron.), that point of the heavens toward which
the earth is moving in its orbit.
Source: Webster’s Unabridged Dictionary 1913 Edition