A Quick Guide to Punctuation for Non-Native Researchers

Punctuation errors rarely make a manuscript incomprehensible, but they do make it harder to read. A misplaced comma changes the rhythm of a sentence. A missing semicolon creates a run-on. Incorrect use of colons, parentheses, or quotation marks signals to reviewers that the manuscript has not been carefully edited.

For non-native English speakers, punctuation is especially tricky because the rules differ between languages. German uses commas before every subordinate clause. Chinese uses different quotation mark styles. Arabic, Hebrew, and other right-to-left languages have entirely different punctuation conventions. If you translate your punctuation habits directly from your first language, errors will follow.

This guide covers the punctuation marks used in academic English, with a focus on the ones that cause the most problems in research manuscripts.

The Period (.)

The period ends a declarative sentence. It is the most basic punctuation mark, and errors are rare. However, non-native speakers sometimes place periods incorrectly after abbreviations. In modern academic English, abbreviations like “et al.” use a period, but abbreviated units (kg, mL, cm) do not. Check your style guide for specific cases.

Use a single space after a period, not two. The two-space convention is a holdover from typewriter-era formatting and is no longer standard in any major style guide.

The Comma (,)

The comma is the most frequently misused punctuation mark in academic writing. Its primary function is to separate elements within a sentence and to indicate a natural pause.

After introductory elements. “After completing the data collection, we began the analysis.” “However, the results were inconclusive.” Always place a comma after introductory words, phrases, or clauses.

In compound sentences. When two independent clauses are joined by a coordinating conjunction (and, but, or, so, yet), place a comma before the conjunction. “The sample size was adequate, and the results were statistically significant.”

In lists. “The study examined age, gender, and education level.” The comma before “and” in a list is the Oxford comma (also called the serial comma). APA and Chicago style require it. AP style does not. In academic writing, the Oxford comma is strongly recommended because it prevents ambiguity. For a detailed discussion, see our post on the Oxford comma.

With non-restrictive clauses. “The participants, who were recruited from three universities, completed an online survey.” The commas indicate that “who were recruited from three universities” is additional information, not essential to identifying the participants. If the clause is restrictive (essential to the meaning), do not use commas: “Participants who scored below 50 were excluded.”

Do not use a comma to join two independent clauses without a conjunction. “The results were significant, further research is needed” is a comma splice. Fix it with a period, a semicolon, or a conjunction.

The Semicolon (;)

The semicolon has two main uses in academic writing. First, it joins two closely related independent clauses without a conjunction. “The first experiment failed to replicate the original findings; the second experiment produced consistent results.” The clauses must be related. If they are not, use a period.

Second, it separates items in a complex list where the items themselves contain commas. “The study was conducted in Kuala Lumpur, Malaysia; Jakarta, Indonesia; and Bangkok, Thailand.” Without semicolons, this sentence would be confusing.

Do not use a semicolon before “and” or “but” in a standard compound sentence. That is the comma’s job.

The Colon (:)

The colon introduces something: a list, an explanation, an elaboration, or a quotation. The text before the colon must be a complete sentence. “The study had three objectives: to identify, to measure, and to evaluate.” Not: “The three objectives were: to identify…” (because “The three objectives were” is not a complete sentence without what follows).

In academic writing, colons are most commonly used to introduce lists, to introduce a block quotation, and between a title and subtitle. “Climate Adaptation in Informal Settlements: A Case Study of Manila.”

Parentheses ( )

Parentheses enclose supplementary information that is useful but not essential to the sentence. In academic writing, their most common uses are for in-text citations (Smith, 2021), for abbreviations on first use (“the World Health Organization (WHO)”), and for brief clarifications (“the second phase (data analysis) took three months”).

Avoid overusing parentheses. If the information in parentheses is important enough to include, consider whether it should be integrated into the sentence instead. Too many parenthetical insertions make sentences choppy and difficult to follow.

Quotation Marks (” “)

In academic writing, quotation marks are used for direct quotations from other sources (with a citation), for technical terms or coined phrases on first use (“the concept of ‘bounded rationality'”), and for titles of articles and chapters (in some citation styles). They are not used for emphasis. If you want to emphasise a word, use italics. Writing “very” important (with quotation marks) actually implies scepticism about the importance, which is the opposite of emphasis.

American English uses double quotation marks (” “) as the default. British English uses single quotation marks (‘ ‘). Check your journal’s convention. For nested quotations, alternate: ‘She said, “The results were significant.”‘

The Apostrophe (‘)

The apostrophe has two main functions: indicating possession and forming contractions. In academic writing, contractions are generally avoided (write “do not” instead of “don’t”), so the primary use is possessive.

For singular nouns, add ‘s: “the researcher’s findings.” For plural nouns ending in s, add only the apostrophe: “the participants’ responses.” For plural nouns not ending in s, add ‘s: “the children’s performance.”

A common error is confusing “its” (possessive: “the study and its limitations”) with “it’s” (contraction of “it is”). In academic writing, you will almost always need “its.”

The Slash (/)

The slash is used sparingly in academic writing. It appears in “and/or,” in fractions (1/4), and in some compound terms (input/output). Avoid using it as a substitute for “or” in running text. “The researcher/participant relationship” is less clear than “the relationship between researcher and participant.”

Conclusion

Punctuation is a small detail that has a large impact on readability. The comma, semicolon, and colon are the three marks that cause the most errors in academic manuscripts by non-native speakers. Master the rules for these three, and most of your punctuation problems will disappear.

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Further Reading

• Overall English Grammar Review for Non-Native Researchers
• Hyphen, En Dash, and Em Dash: What Is the Difference?
• What Is the Oxford Comma and How Do We Use It?
• Capitalization Rules in English: A Guide

Frequently Asked Questions

What is the difference between a comma and a semicolon?

A comma separates elements within a sentence: items in a list, introductory phrases, or clauses joined by a conjunction. A semicolon joins two closely related independent clauses without a conjunction. If you can replace the semicolon with a period and both sentences still work, the semicolon is correct. If one side is not a complete sentence, use a comma or colon instead.

Should I use the Oxford comma in academic writing?

Yes, in most cases. APA, Chicago, and most academic style guides require the Oxford comma (the comma before “and” in a list of three or more items). It prevents ambiguity. “The study examined age, gender, and income” is clearer than “age, gender and income,” which could be misread as treating “gender and income” as a single item.

When should I use quotation marks in academic writing?

Use quotation marks for direct quotes from sources (with a citation), for technical terms or coined phrases on first use, and for article or chapter titles in some citation styles. Do not use quotation marks for emphasis. Use italics instead. Quotation marks around a word for emphasis can imply scepticism or irony, which is usually not the intended effect.

Is it acceptable to use contractions in academic writing?

No, contractions (don’t, can’t, it’s, won’t) are generally avoided in formal academic writing. Write the full forms: do not, cannot, it is, will not. Some style guides and journals are becoming more relaxed about this, but the safe default for journal submissions and theses is to avoid contractions entirely.