Comma

Use a comma

• to separate the elements in a series. Even though in British English, a comma is usually not placed before and, it is quite common in academic writing.

Age, sex and socioeconomic status were equated for subjects of the four treatment conditions.
Age, sex, and socioeconomic status were equated for subjects of the four treatment conditions.

• to separate independent clauses joined by a coordinating conjunction (and, but, either, neither, or nor). The comma may be omitted if the two clauses are short and no ambiguity will result.

The amount of job satisfaction increased, but the rate of production dropped.

• after a subordinate clause (if, although, since, when, where, while, because, etc.) or participle clause

Although the results were not significant, the study suggests some ideas for further research.
Encouraged by these results, we conducted an additional analysis.

• to set off non-restrictive clauses from the rest of the sentence. Nonrestrictive clauses give extra information that is not essential to the meaning of the sentence.

The switch, which was attached to the panel, controlled the stimulus light.

• to separate transitions (therefore, thus, however, consequently) from the rest of the sentence.

The only alternative, therefore, is to repeat the experiment.

• to separate words, clauses, or phrases that interrupt the direct movement of the sentence.

Electrical shock, except at extremely high voltage, provides an effective negative enforcement.

• in dates (January, 3, 1996), names (William A. Brooks, Esq.) and addresses (London, UK).

 

Do not use a comma

• after a subject of a clause, even if it is long. There should never be a comma between a subject and its verb.

The only computation to be performed is the admission control test.

• before a subordinate clause, except if the subordinate clause is non-restrictive

Inflation will change because the exchange rate will eventually return to its long-run level.

But in no case can the method establish its truth, even if it is true. (could be left out)

• before or after restrictive elements, for instance restrictive relative clauses or restrictive participle clauses

The person who first launched this idea was ridiculed by his colleagues.

• after an adverb which modifies one particular word rather than the entire sentence

Particularly article 16 is worth mentioning.

• Between two independent sentences: this is called a comma splice. Instead of a comma, use a full stop, a colon, or a semi-colon. More information on the comma splice

*Again, the difference between the versions is in the expected direction, however in this case the difference is statistically significant.

Again, the difference between the versions is in the expected direction. However, in this case the difference is statistically significant.