commas to prevent misreading

A comma follows an introductory clause when the noun after it could be interpreted as the clause’s object: While the chef cooked, the waiters set the tables. Without the comma, cooked the waiters reads as a verb and its object until set shows the error.

A comma also follows an introductory adverb that could read as a preposition: Inside, the dog was barking. Without it, inside the dog reads as a prepositional phrase until was shows the error.

A comma before a conjunction that joins two independent clauses keeps a reader from interpreting the second subject as part of a compound object: She painted the walls, and the ceiling stayed white. Without the comma, the walls and the ceiling reads as one compound object of painted until stayed shows the error.

No comma may separate a subject from its verb, even to prevent a misreading; rewrite the sentence instead. In Employees who complain often get fired, often could modify either complain or get fired. A comma after complain would tie often to get fired, but it would separate the subject Employees who complain from its verb get. Recast so the adverb can modify only one verb: Employees who often complain get fired or Employees who complain are often fired.

See also comma with introductory elements; prepositional phrases: when to use commas; comma before a coordinating conjunction; comma.