nex·us 
(nĕksəs)
(nĕksəs)n. pl. nexus or nex·us·es
1. A means of connection; a link or tie: "this nexus between New York's ... real-estate investors and its ... politicians" (Wall Street Journal).
2. A connected series or group.
3. The core or center: "The real nexus of the money culture [was] Wall Street" (Bill Barol).
[Latin, from past participle of nectere, to bind; see ned- in the Appendix of Indo-European roots.]