nexus

noun

• A form of connection.
• A connected group.
• The centre of something.
• In Ancient Rome, a person who had contracted a nexum or obligation of such a kind that, if he failed to pay, his creditor could compel him to work as a servant until the debt was paid.
• The relationship between a vendor and a jurisdiction for the purpose of taxation, established for example by the vendor operating a physical store in that jurisdiction.