Semicolon
The semicolon should be used when the independent clauses (complete sentences) combine to convey a single thought. The semicolon balances two equally weighted elements. Some editors do not like semicolons in dialogue, but many published authors (and some editors) believe a semicolon is acceptable in dialogue; however, it shouldn’t be used in dialogue without good reason.

There are no spaces before a semicolon and a single space after it. The second independent clause (complete sentence) isn’t capitalized.

Usage
1. Semicolons can (and frequently should) be used in place of commas to clarify lists of items that contain internal commas

Example: At the party, I met George, the mayor; Margaret, the mayor’s cranky assistant; and Barbara, a published author.

2. Semicolons can be used between closely related independent clauses (complete sentences) that are not linked by a coordinating conjunction (for, and, nor, but, or, yet, so)

Example: Last year, he couldn’t get a job at a greasy spoon; today, he’s a gourmet chef.

3. A semicolon can be used to emphasize a contrast

Example: Winters were too cold; summers were too hot.

4. When a conjunctive adverb is used to transition between independent clauses (complete sentences), a semicolon introduces the conjunctive adverb

Example: Bobby thought he could use the rocks to cross the creek; however, when he tried, he fell in.