In mathematics, the phrase almost all has a number of specialised uses. "Almost all" is sometimes used synonymously with "all but finitely many" or "all but a countable set"; see almost. An example of this usage is the Frivolous Theorem of Arithmetic, which states that almost all natural numbers are very, very, very large. When speaking about the reals, sometimes it means "all reals but a set of Lebesgue measure zero". In this sense we can say "almost all reals are not a member of the Cantor set"