connexion vs phone line

connexion and phone line both are nouns.

Word	Noun	Adjective	Verb	Adverb
connexion	Yes	No	No	No
phone line	Yes	No	No	No

As nouns, phone line is a hyponym of connexion; that is, phone line is a word with a more specific, narrower meaning than connexion:

connexion (noun)	phone line (noun)
the act of bringing two things into contact (especially for communication)	a telephone connection
shifting from one form of transportation to another
an instrumentality that connects
the process of bringing ideas or events together in memory or imagination
a relation between things or events (as in the case of one causing the other or sharing features with it)
a connecting shape