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Section 8.2.9

Superfluous Commas

Except after an introductory dependent clause, do not use a comma to separate a dependent clause from a main clause unless the dependent clause provides nonessential information. See also Restrictive and Nonrestrictive Modifiers.


Unacceptable

Ever since the atomistic view of matter came to be accepted, it has been a burning question, how to see into the microworld of molecular chemistry.

Acceptable

Ever since the atomistic view of matter came to be accepted, it has been a burning question how to see into the microworld of molecular chemistry.

--Adapted from Philip Ball, Designing the Molecular World


Do not set off a clause that is essential to the sentence. Such clauses often begin with that.


Unacceptable

Systematic surveys of the ocean floor revealed, that there were submarine mountain ranges, that extended for thousands of kilometers.

Acceptable

Systematic surveys of the ocean floor revealed that there were submarine mountain ranges that extended for thousands of kilometers.


Do not use a comma to separate the subject from the rest of the sentence.


Unacceptable

A biosensor that produces a changing electrical signal in response to levels of glucose in the bloodstream of diabetics, could be used to control the release of insulin so as to maintain the concentration of blood sugar at a steady, safe level.

Acceptable

A biosensor that produces a changing electrical signal in response to levels of glucose in the bloodstream of diabetics could be used to control the release of insulin so as to maintain the concentration of blood sugar at a steady, safe level.

--Adapted from Philip Ball, Designing the Molecular World


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