linkage vs nexus

linkage and nexus both are nouns.

Word	Noun	Adjective	Verb	Adverb
linkage	Yes	No	No	No
nexus	Yes	No	No	No

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

Other hyponyms of linkage include link.

linkage (noun)	nexus (noun)
the act of linking things together	a connected series or group
a mechanical system of rods or springs or pivots that transmits power or motion	the means of connection between things linked in series
(genetics) traits that tend to be inherited together as a consequence of an association between their genes; all of the genes of a given chromosome are linked (where one goes they all go)
an associative relation