Many systems have processes with time-lag in their behaviour.
Changes to systems’ behaviour do not occur immediately when a change to the inputs or transformation process is made.
Changes can take significant amount of time to take effect, therefore can be difficult to predict system behaviour.
Unintended changes might not become apparent for significant amount of time e.g. human activity never considered cause of global warming until some effects of global warming were noticed.
Has consequences for feedback control mechanisms and how long they will need to take effect.