linkage (Noun) — An associative relation.
linkage (Noun) — (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).
linkage (Noun) — A mechanical system of rods or springs or pivots that transmits power or motion.
linkage (Noun) — The act of linking things together.