What joins two independent clauses if a conjunction is not used?

If a conjunction isn't used to join two independent clauses, a semicolon (;) is used.

Here's an example:

* The rain was pouring; the wind howled fiercely.

Note: You can also use a colon (:) to join two independent clauses, but only if the second clause explains or expands on the first clause.

Here's an example:

* The dog barked loudly; it was trying to warn us of danger.