paired with a body, the heading of the relation being also the heading of each tuple in its body. The number of attributes constituting a heading is called the degree, which term also applies to tuples and relations. The term n-tuple refers to a tuple of degree n (n >= 0).

E. F. Codd used the term "relation" in its mathematical sense of a finitary relation, a set of tuples on some set of n sets S₁,S₂,....,S_n. Thus,