  We analyse abstract data types that model numerical structures with a concept
of error. Specifically, we focus on arithmetic data types that contain an error
value $\bot$ whose main purpose is to always return a value for division. To
rings and fields, we add a division operator $x/y$ and study a class of
algebras called common meadows wherein $x/0 = \bot$. The set of equations true
in all common meadows is named the equational theory of common meadows. We give
a finite equational axiomatisation of the equational theory of common meadows
and prove that it is complete and that the equational theory is decidable.
