Semicolons

Rule #1
Use a semicolon to separate two independent clauses.
Example:
Some french fries are greasy; some are not.

Rule #2
Use a semicolon before conjunctive adverbs when they are used to join independent clauses.
Conjunctive adverbs:
also, consequently, nevertheless, therefore, then, still, however
Example:
Some french fries are greasy; however, others are not.

General Rule:
Semicolons connect units of equal grammatical rank.