convergence vs joining

convergence and joining both are nouns.

Word	Noun	Adjective	Verb	Adverb
convergence	Yes	No	No	No
joining	Yes	No	No	No

As nouns, joining is a hypernym of convergence; that is, joining is a word with a broader meaning than convergence:

convergence: the act of converging (coming closer)
joining: the act of bringing two things into contact (especially for communication)

Other hypernyms of convergence include connection, connexion.

convergence (noun)	joining (noun)
the act of converging (coming closer)	the act of bringing two things into contact (especially for communication)
the approach of an infinite series to a finite limit
a representation of common ground between theories or phenomena
the occurrence of two or more things coming together