Let
be a sequence of events in some sample space
. Let
be an outcome.
In the following table, all statements in the "infinitely often" column are logically equivalent. Similarly, all statements in the "almost always" column are logically equivalent.
| perspective |
infinitely often |
almost always
|
| unions and intersections |
 |
|
| first-order quantifiers |
 |
|
| verbal expression |
for infinitely many  |
for almost all , i.e. for all but finitely many , i.e. for finitely many
|
| lim sup/lim inf |
 |
|
| limit of sup/inf |
 |
|
Analogy with sequences of real numbers
Let
be a sequence of real numbers, and let
be a real number.
We say
is eventually
-close to
iff there exists some
such that for all
we have
.
We say that
is continually
-adherent iff for every
there exists some
such that
.
I think we can even define
.