  We consider several ternary algebras relevant to physics. We compare and
contrast the quantal versions of the algebras, as realized through associative
products of operators, with their classical counterparts, as realized through
classical Nambu brackets. In some cases involving infinite algebras, we show
the classical limit may be obtained by a contraction of the quantal algebra,
and then explicitly realized through classical brackets. We illustrate this
classical-contraction method by the Virasoro-Witt example.
