A more thorough explanation:

Definition: A connection or link, often a causal one.

Example: Cigarette packages must inform consumers of the nexus between smoking and lung cancer.

Explanation: This means that there is a connection or link between smoking and lung cancer, and that smoking can cause lung cancer. The example shows that cigarette packages must inform consumers of this connection so that they are aware of the risks associated with smoking.

Plural: Nexuses or nexus.

Additional definition: In Roman law, a debtor given in bondage to creditors until the debts have been paid. This practice was allowed in very early Roman law and was called nexum. It reduced debtors to a sort of slavery, and many literary texts dealt with debtors who were nexi. However, it went out of use after a law was passed requiring an actual judgment before seizure.