|(database)||functional dependency - Given a relation R (in a relational database),
attribute Y of R is functionally dependent on attribute X of R
and X of R functionally determines Y of R (in symbols R.X ->
R.Y) if and only if each X in R has associated with it
precisely one Y in R (at any one time). Attributes X and Y
may be composite.|
This is very close to a function in the mathematical sense.