Bad Commas

Commas are used to separate things, but some things should not be separated. Today we will examine four cases where commas should not be used.

Case #1: Compound Subjects

If your sentence has two subjects and one verb, don’t use a comma to separate the subjects.

Bad Comma Example:

The logging crew, and the petrophysicist, left the wellsite at 6 p.m.

Here, the two subjects are “the logging crew” and “the petrophysicist.” They both left at the same time with the same verb, so you don’t need the commas to separate them.

Case #2: Compound Verbs

If your sentence has one subject and two verbs, don’t use a comma to separate the verbs.

Bad Comma Example:

In such carbonate systems, log-derived water saturation techniques fail to compensate for microporosity, and misrepresent movable hydrocarbon pore volumes.

Here, the subject, “water saturation techniques,” does two things: “fail to compensate” and “misrepresent.” You do not need a comma separating them, so lose the comma after “microporosity.
Case #3: Compound Objects

If your sentence has one verb and two object, whether direct objects or indirect objects, don’t use a comma to separate the objects.

Bad Comma Examples:

This impacts porosity, and permeability. (direct objects)

The manager could give the geologist, or the petrophysicist, a raise. (indirect objects)

Nix on the commas in both these sentences.

Case #4: Multiple Objects of the Preposition

If your sentence has two or more objects of the same preposition, don’t use a comma to separate the objects.

Bad Comma Example:

Saturation-height models cannot discriminate between capillary-bound water in microporosity, and moveable water.

Here, the preposition is “between,” and its two objects are “capillary-bound water” and ” moveable water.” You do not need a comma separating them, so lose the comma after “microporosity.”

You do need a comma to separate a compound sentence, which has two subjects, each with its own verb or verbs, and probably an object or two thrown in for good measure.

Good Comma Example:

The petrophysicist submitted the report to the technical writer, and she cleaned it up and formatted it so it would impress the manager.

Here, the subject and verb of the first part of this compound sentence are “petrophysicist” and “submitted,” respectively. The subject of the second part of the compound sentence is “she,” and the compound verb is “cleaned” and “formatted.” If you separated these two parts (and removed the conjunction “and,”) they would stand alone as complete sentences. That’s when you need a comma: to separate two complete thoughts.
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Comma Quote of the Day:

“This morning I took out a comma, and this afternoon I put it back in again.”

– Oscar Wilde, American playwright / novelist / poet, 1854-1900

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