link vs join

link and join both are nouns.

Word	Noun	Adjective	Verb	Adverb
link	Yes	No	Yes	No
join	Yes	No	Yes	No

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

link: a connecting shape
join: the shape or manner in which things come together and a connection is made

Other hyponyms of link include node, articulation, joint, junction, juncture.

As verbs, join is a hyponym of link; that is, join is a word with a more specific, narrower meaning than link:

As verbs, link and join are synonyms defined as:

Other synonyms of link include connect, link up, unite.

link (noun)	join (noun)
a fastener that serves to join or connect	a set containing all and only the members of two or more given sets
a two-way radio communication system (usually microwave); part of a more extensive telecommunication network	the shape or manner in which things come together and a connection is made
an interconnecting circuit between two or more locations for the purpose of transmitting and receiving data
a channel for communication between groups
(computing) an instruction that connects one part of a program or an element on a list to another program or list
a unit of length equal to 1/100 of a chain
the means of connection between things linked in series
a connecting shape
the state of being connected

link (verb)	join (verb)
make a logical or causal connection	make contact or come together
connect, fasten, or put together two or more pieces	cause to become joined or linked
link with or as with a yoke	become part of; become a member of a group or organization
be or become joined or united or linked	come into the company of
	be or become joined or united or linked