"Nexus is the term used for everything as a whole." And apparently not in use in other universes and timelines. "Which would include every system, its planets and wormholes leading between included."

He uses his fork to gesture at the space around them. "You're already seeing how it complicates. There's only one wormhole that reaches Barrayar with the closest colonized planet five jumps away. No one else will send fleets to aid or stop what's happening here."

Partially because they'd have to deal with Duv's home planet's space to reach access. Politics.