Commas

1 With conjunctions

Commas are not usually used with coordinating conjunctions like the following. A comma would reflect more intonation (in speaking) for emphasis, and in writing this looks colloquial.

• But
• So
• Then
• And

For example:

X But, statistics show the greatest escape rates from poverty by welfare benefits.

✔️ But statistics show the greatest escape rates from poverty by welfare benefits.

X So, it is necessary to research the effects of cultural factors on English learning, including Korean culture.

✔️ So it is necessary to research the effects of cultural factors on English learning, including Korean culture.

X Then, they might have some problems in making various kinds of English sentences, because they tend to make easy, short sentences to avoid making grammar mistakes.

✔️ Then they might have some problems in making various kinds of English sentences, because they tend to make easy, short sentences to avoid making grammar mistakes.

It would be fine in formal writing to use a comma with these, if some other material comes between the conjunction and the sentence subject.

• But, as a recent report indicates, statistics show the greatest escape rates from poverty by welfare benefits.
• But, as we demonstrated in a previous paper, statistics show the greatest escape rates from poverty by welfare benefits.=== Style variations ===

1.1 With conjunctive adverbials

The following conjunctions are known as conjunctive adverbs / adverbials – originally adverbs, they came to be used like sentence at the start of clauses.

• however, therefore, furthermore, otherwise, moreover

These are preceded by a full stop (period or semicolon) and followed by a comma.

• The result means the preschooler’s capacity for language skills is affected by age. However, at this point they are all preschoolers, so higher scores for older ages may not be meaningful.
• The result means the preschooler’s capacity for language skills is affected by age; however, at this point they are all preschoolers, so higher scores for older ages may not be meaningful.
• Participants found specific cues to be helpful for the task. Furthermore, higher proficiency L2 learners may be more aware of visible speech cues and better able to make use of them.

Some connectors can come after the sentence subject or other phrase, i.e., not in sentence-initial position. How do these affect the flow? (Note that thus does not necessarily require commas when non-initial.)

• As an adult, however, learning a foreign language was his own decision, and so that strong motivation was essential to maintain and achieve his goals.
• The historical evidence thus does not support the standard hypothesis.
• Bilingual education at the preschool level is therefore quite effective.

1. Some connectors can come after the sentence subject or other phrase, i.e., not in sentence-initial position. How do these affect the flow? (Note that thus does not necessarily require commas when non-initial.)
2. As an adult, however, learning a foreign language was his own decision, and so that strong motivation was essential to maintain and achieve his goals.
3. Unlike the traditional research findings, however, instrumentality was not as significant a variable as for other age groups.
4. The historical evidence thus does not support the standard hypothesis.
5. Bilingual education at the preschool level is therefore quite effective. Comma splices, or fused sentences

2 Comma splices

A comma splice refers to a sentence with clauses simply joined by a comma, without an appropriate conjunction or other transitional. Instead, a transitional should be used, or a semi-colon or period. Compare the following versions of a sentence; the first has a comma splice, resulting in what we called a fused sentence.

X Typically, graduate student receive good grades, their social lives rate as a C−.

1. Typically, graduate student receive good grades, but their social lives rate as a C−.
2. Typically, graduate student receive good grades; their social lives rate as a C−.
3. Typically, graduate student receive good grades; however, their social lives rate as a C−.
4. Although graduate student typically receive good grades, their social lives rate as a C−.