friend vs subscriber

friend and subscriber both are nouns.

Word	Noun	Adjective	Verb	Adverb
friend	Yes	No	No	No
subscriber	Yes	No	No	No

As nouns, subscriber is a hyponym of friend; that is, subscriber is a word with a more specific, narrower meaning than friend:

friend (noun)	subscriber (noun)
a person you know well and regard with affection and trust	someone who contributes (or promises to contribute) a sum of money
a person with whom you are acquainted	someone who contracts to receive and pay for a service or a certain number of issues of a publication
an associate who provides cooperation or assistance	someone who expresses strong approval
a person who backs a politician or a team etc.