We define a simple non-deterministic functional language that has defi
nite variables and where function application is unfoldable. This lang
uage demonstrates that Sondergaard and Sestoft's claim, that in a non-
deterministic language we cannot obtain both definiteness and unfoldab
ility, assumes a fairly general notion of non-determinism. Our languag
e relies on using a restricted notion of non-determinism called partia
l determinism.