isogonic line vs isogone

isogonic line and isogone both are nouns.

Word	Noun	Adjective	Verb	Adverb
isogonic line	Yes	No	No	No
isogone	Yes	No	No	No

As nouns, isogonic line and isogone are synonyms defined as:

isogonic line and isogone: an imaginary line connecting points on the Earth's surface where the magnetic declination is the same

Other synonyms of isogonic line include isogonal line.

isogonic line (noun)	isogone (noun)
an imaginary line connecting points on the Earth's surface where the magnetic declination is the same	an imaginary line connecting points on the Earth's surface where the magnetic declination is the same