noun

• (chiefly in the plural) A relationship; the manner in which and tone with which people or states, etc. interact.
  "the foreign relations of the United States"
• (set theory) A set of ordered tuples.
  "[…]Signs are, first of all, physical things: for example, chalk marks on a blackboard, pencil or ink marks on paper, sound waves produced in a human throat. According to Reichenbach, "What makes them signs is the intermediary position they occupy between an object and a sign user, i.e., a person." For a sign to be a sign, or to function as such, it is necessary that the person take account of the object it designates. Thus, anything in nature may or may not be a sign, depending on a person's attitude toward it. A physical thing is a sign when it appears as a substitute for, or representation of, the object for which it stands with respect to the sign user. The three-place relation between sign, object, and sign user is called the sign relation or relation of denotation."
• (set theory) A set of ordered tuples.
  "Equality is a symmetric relation, while divisibility is not."
• (databases) A set of tuples, implemented as a table in a relational database.
  "This relation uses the customer's social security number as a key."