(informal) Something or someone that doesn't quite make it.

Very close to, but not quite. / (mathematics) Up to, except for a negligible set (where negligible is not universally but contextually defined).

plural of almost

The quality of almost being something, or almost reaching a point; incomplete state.

(measure theory) For all elements except those contained in some set of measure zero. / Used other than figuratively or idiomatically: see almost, everywhere.

(mathematics) All, except for a negligible set, i.e. finite, countable or of measure zero. / Used other than figuratively or idiomatically: see almost, all.

(probability theory) With probability equal to one.

plural of almost prime

(number theory) A natural number for which there exists an absolute constant K such that the number has at most K prime factors.

(number theory) Having this property.