aphelion

UK: /æpˈhiːlɪən/

US: /əˈfiliən/

US: (ə fē′lē ən, ə fēl′yən, ap hē′lē ən)

Inflections of 'aphelion' (n): npl: aphelia

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

a•phe•li•on /əˈfiliən/   n. [countable] , pl. a•phe•li•a 

/əˈfiliə/.  
1. Astronomy the point in the orbit of a planet or a comet when it is farthest from the sun.Compareperihelion.

See -helio-.

WordReference Random House Unabridged Dictionary of American English © 2025

a•phe•li•on  (ə fē′lē ən, ə fēl′yən, ap hē′lē ən), n., pl. a•phe•li•a 

(ə fē′lē ə, ə fēl′yə, ap hē′lē ə). 
1. Astronomy the point in the orbit of a planet or a comet at which it is farthest from the sun. Cf. perihelion.

• Greek *aphé̄lion (diástēma) off-sun (distance), neuter of *aphé̄lios (adjective, adjectival), equivalent. to ap- ap-² + hé̄li(os) sun + -os adjective, adjectival suffix. See apogee
• Hellenized form of Neo-Latin aphēlium 1650–60

a•phe′li•an, adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

aphelion / æpˈhiːlɪən əˈfiː-/ noun ( -lia / -lɪə/)

1. the point in its orbit when a planet or comet is at its greatest distance from the sun
   Compare perihelion

Etymology: 17th Century: from New Latin aphēlium (with pseudo-Greek ending -ion) from ap- + Greek hēlios sun