1.  nexus(n = noun.linkdef) link - the means of connection between things linked in series;
is a kind of linkage

2.  nexus(n = noun.group) - a connected series or group;
is a kind of series

   Connection; tie. [1913 Webster]
"Man is doubtless one by some subtile nexus . . . extending from the new-born infant to the superannuated dotard." [1913 Webster]

nexus, n. (pl. same)
1 a connected group or series.
2 a bond; a connection.

Etymology:
L f. nectere nex- bind