The \emph{residual size} of a class of algebraic structures is the supremum of the cardinalities of the
[[subdirectly irreducible]] members of the class. If there is no bound on the size of the subdirectly irreducible
members, the residual size is said to be \emph{unbounded}. In this case the class is said to be \emph{residually large}, 
otherwise it is \emph{residually small}. If all subdirectly irreducible members are finite, the class is \emph{residually finite}.