Much-greater-or-less

Summary

Means "much less than" and "much greater than". Generally, much is not formally defined, but means that the lesser quantity can be neglected with respect to the other. This is generally the case when the lesser quantity is smaller than the other by one or several orders of magnitude.

In measure theory, $\mu\ll\nu$ means that the measure $\mu$ is absolutely continuous with respect to the measure $\nu$.