The Relation is the basic element in a relational data model.

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  1. Relation (file, table) is a two-dimensional table.
  2. Attribute (i.e. field or data item) is a column in the table.
  3. Values in a column all have the same meaning.
  4. Tuple (i.e. record) is a row in the table.
  5. Values of a row all relate to some thing or portion of thing.
  6. Duplicate rows are not allowed.
  7. Cells must be single-valued (but can be variable length).