The Nexus is not in the orignial Smackdown vs Raw roster, but three members from the old Nexus (Wade Barrett, Justin Gabriel and David Otunga) can be bought and downloaded in the first DLC pack from...
Either way, depending on context. But anyway, in plain speech it is better to use an English word, like bond or connection, instead. Nexus is fun to say, but hard to use without sounding silly or...