Semicolon Before Conjunction When Clauses Are Long with Internal Commas
The Semicolon
Rulebase Summary
Use a semicolon (rather than just a comma) before a coordinating conjunction (and, but, or, nor) joining two independent clauses when either clause is very long and already contains commas. The semicolon provides a stronger visual break, preventing the conjunction's comma from getting lost among the internal commas.
Examples
A. The driver, who was intoxicated, ran the stop sign at Oak and Elm, and the passenger, who was not wearing a seatbelt, was ejected from the vehicle.
A. The driver, who was intoxicated, ran the stop sign at Oak and Elm; and the passenger, who was not wearing a seatbelt, was ejected from the vehicle.
Semicolon before 'and' when both clauses have internal commas.
A. The first witness, Dr. Harris, disagreed, but the second witness, Dr. Cho, agreed.
A. The first witness, Dr. Harris, disagreed; but the second witness, Dr. Cho, agreed.
Internal commas make the conjunction comma invisible — upgrade to semicolon.
Style Guide References (2)
Morson's
BGGP