No Omission Comma When Parallel Sentences Are Joined by a Conjunction
The Comma
Rulebase Summary
When two parallel sentences are joined by a coordinate conjunction, do not use a comma before the conjunction (because there is no independent subject and verb in the second part), and do not use a comma of omission for elements present in the first sentence but absent from the second. The comma of omission applies only when parallel clauses are joined by a semicolon without a conjunction — not when a conjunction links them.
Examples
A. The plaintiff filed the motion on Monday, and the defendant, on Thursday.
A. The plaintiff filed the motion on Monday and the defendant on Thursday.
No comma before 'and' (no independent subject-verb after it) and no comma of omission.
A. Her claim was for damages, but his, for an injunction.
A. Her claim was for damages but his for an injunction.
No comma before 'but' and no omission comma — the conjunction links parallel elements, not independent clauses.
Transcript Notes
The comma of omission is always inserted for something present in the first part of the sentence that is missing in the second part. However, the comma is used ONLY when there is parallel construction with a semicolon between the clauses and no coordinate conjunction.
When a coordinate conjunction links two clauses and the second clause lacks an independent subject and verb, no comma goes before the conjunction — and no comma of omission is used.
When the conjunction links two full independent clauses, a comma does go before the conjunction.
Style Guide References (1)
BGGP