Apparently I've been confused about the meaning(s) of "chaotic behavior". I always thought it meant that infinitesimal perturbations of a system parameter would lead to large changes in the system's behavior, and thus that the behavior of the system is effectively unpredictable even though it might be deterministic.

More recently, though, I get the impression that sometimes "chaotic behavior" has a second definition in which it simply means "aperiodic behavior". This from the paper, Complexity in Linear Systems .... Perhaps there are additional definitions of "chaotic behavior". But: would deterministic aperiodic behavior be effectively unpredictable in the same sense as the unpredictability per the first definition?