Using Apostrophes in Scientific Writing: Examples, Tips, Rules

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Apostrophes are small punctuation marks that can have a significant impact on clarity and professionalism. In research papers or dissertations, they are used much less frequently than in general writing because academic style favors precision, objectivity, and formal language.

This guide explains when apostrophes should and should not be used in research papers, theses, dissertations, grant proposals, and scientific reports.

Contents

• Why apostrophes matter
• The two main uses of apostrophes
• Apostrophes for possession
• Contractions in scientific writing
• Apostrophes and abbreviations
• Apostrophes in species names
• Apostrophes in units and symbols
• Common Mistakes in Apostrophe Usage
• Apostrophe versus Prime Sign (′)
• Quick editing checklist for apostrophe usage
• Key takeaways

Why apostrophes matter

Correct apostrophe usage helps readers distinguish between:

• Possession
• Contractions
• Plurals

Misusing apostrophes is one of the most common punctuation errors in manuscripts.

The two main uses of apostrophes

Use	Example
Showing possession	the patient’s symptoms
Forming contractions	don’t, it’s

In scientific writing, contractions are generally avoided, so most apostrophes indicate possession.

Apostrophes for possession

Singular nouns

Add ‘s to singular nouns.

Correct	Incorrect
the author’s hypothesis	the author hypothesis
the participant’s response	the participants response
the cell’s membrane	the cells membrane
the specimen’s weight	the specimen weight

Examples

• The patient’s blood pressure was monitored continuously.
• The virus’s genome was sequenced.

• The sample’s temperature increased rapidly.
• The detector’s sensitivity improved.

• The participant’s responses were coded.
• The teacher’s observations supported the findings.

Singular nouns ending in s

Most scientific style guides recommend adding ‘s.

Preferred	Also seen
James’s experiment	James’ experiment
Harris’s model	Harris’ model

Follow your journal’s preferred style consistently.

Plural nouns ending in s

Add only an apostrophe.

Correct	Incorrect
the researchers’ conclusions	the researchers’s conclusions
the patients’ records	the patient’s records (if multiple patients)
the students’ essays	the student’s essays

Examples

• The researchers’ interpretation differed from previous studies.
• The patients’ outcomes were assessed after six months.

Irregular plural nouns

Add ‘s.

Correct
children’s development
women’s health
men’s attitudes
people’s perceptions

Examples

• Children’s nutritional status improved significantly.
• Women’s participation increased over time.

Possessive pronouns do NOT use apostrophes

This is among the most common mistakes.

Correct	Incorrect
its	it’s
yours	your’s
theirs	their’s
ours	our’s
whose	who’s (unless meaning “who is”)

Examples

✔ The instrument reached its maximum operating temperature.

✘ The instrument reached it’s maximum operating temperature.

Its versus it’s

This is the most frequently confused pair.

Word	Meaning
its	belonging to it
it’s	it is or it has

Correct

• The protein lost its function.
• It’s important to calibrate the equipment.

Incorrect

• The protein lost it’s function.
• Its important to calibrate the equipment.

Quick test

Replace it’s with it is.

If the sentence still makes sense, use it’s.

Whose versus who’s

Word	Meaning
whose	possessive
who’s	who is

Examples

✔ Researchers whose data met the criteria were included.

✔ Who’s responsible for the laboratory inventory?

Apostrophes with names

Add ‘s to most names.

Correct
Newton’s laws
Darwin’s theory
Fisher’s exact test
Pearson’s correlation coefficient

Examples

• Newton’s second law explains acceleration.
• Fisher’s exact test was used for small sample sizes.

Apostrophes with organizations

Organizations can be possessive.

Examples

• The university’s ethics committee approved the study.
• The journal’s guidelines were followed.
• The laboratory’s equipment was upgraded.

Compound nouns

Add the apostrophe to the final word.

Correct
the editor-in-chief’s decision
my PhD supervisor’s recommendation
the director of research’s comments

Joint possession

When two people own something together, add the apostrophe only to the last name.

Correct
Smith and Jones’s study

If each owns something separately, both receive apostrophes.

Correct
Smith’s and Jones’s laboratories

Time and measurement expressions

Time expressions often take possessive apostrophes.

Correct
one year’s follow-up
two weeks’ notice
three months’ observation
five years’ experience

Examples

• Participants completed one year’s follow-up.
• The study involved three months’ observation.

Scientific terminology that uses apostrophes

Some scientific terms traditionally contain apostrophes.

Examples
Parkinson’s disease
Alzheimer’s disease
Hodgkin’s lymphoma
Euler’s equation
Fourier’s law
Hooke’s law
Avogadro’s constant (older usage varies)

Always follow the terminology preferred by your target journal or discipline.

Contractions in scientific writing

Formal scientific writing usually avoids contractions.

Informal	Formal
don’t	do not
can’t	cannot
isn’t	is not
doesn’t	does not
weren’t	were not
we’ve	we have

Less formal

• We didn’t observe any differences.

Preferred

• We did not observe any differences.

Apostrophes and abbreviations

Possession is acceptable.

Correct
DNA’s structure
MRI’s limitations
PCR’s sensitivity

However, many editors prefer rewording.

Instead of:

• DNA’s structure

Use:

• the structure of DNA

This often sounds more formal.

Apostrophes in species names

Scientific names themselves do not use apostrophes.

Correct
Escherichia coli
Arabidopsis thaliana
Drosophila melanogaster

Possession is expressed normally.

• E. coli‘s growth rate
• the growth rate of E. coli

The second construction is generally preferred.

Apostrophes in units and symbols

Units never take apostrophes.

Correct	Incorrect
10 kg	10 kg’s
5 cm	5 cm’s
20 mL	20 mL’s

Apostrophes are NOT used for plurals

Never use apostrophes simply to make a word plural.

Correct	Incorrect
tables	table’s
figures	figure’s
assays	assay’s
samples	sample’s

Plurals of abbreviations

Most style guides do not use apostrophes.

Correct	Less preferred
PCRs	PCR’s
MRIs	MRI’s
PhDs	PhD’s
RCTs	RCT’s

Plurals of numbers

No apostrophe.

Correct	Incorrect
the 1990s	the 1990’s
three 7s	three 7’s
the 2000s	the 2000’s

Common Mistakes in Apostrophe Usage

Incorrect	Correct
it’s role	its role
the student’s participated	the students participated
three sample’s	three samples
researchers finding’s	researchers’ findings
the journals policy	the journal’s policy
patient’s were enrolled	patients were enrolled
PCR’s were performed	PCRs were performed

Apostrophe versus Prime Sign (′)

Although the apostrophe (’) and the prime sign (′) look similar, they serve entirely different purposes. In scientific writing, using the correct character is important because many journals and publishers distinguish between them.

Apostrophe (’)	Prime sign (′)
Indicates possession or contractions	Indicates units, derivatives, labels, or mathematical notation
Punctuation mark	Mathematical or scientific symbol
Example: the author’s data	Example: 35′, f′(x)

When to use the prime sign

1. Minutes of angle

The prime sign denotes arcminutes in angular measurements.

Correct	Meaning
45° 30′	45 degrees, 30 arcminutes
18′	18 arcminutes

Example

• The telescope was aligned within 2′ of the target position.

2. Minutes of time

The prime sign also represents minutes when expressing time in certain scientific disciplines, especially astronomy and navigation.

Correct
12′ 30″
5′

3. Feet and inches

Outside academic writing, the prime sign is widely used for feet and inches.

Correct
6′ 2″
5′ 10″

Although this notation is common, many scientific journals prefer SI units (meters or centimeters) instead.

4. Mathematics

The prime sign commonly indicates derivatives or modified variables.

Correct	Meaning
f′(x)	First derivative
y′	Derivative of y
x′	A transformed or related variable
A′	A modified point or object

Example

• The function f′(x) reached zero at the critical point.

5. Physics and engineering

Prime symbols distinguish related quantities.

Examples include:

• T′
• V′
• E′
• P′

These often represent transformed, corrected, estimated, or secondary variables.

6. Molecular biology and genetics

Prime notation identifies the orientation of nucleic acid strands.

Correct
5′ end
3′ end
5′→3′ direction

Example

• DNA polymerase synthesizes DNA in the 5′→3′ direction.

Do not substitute an apostrophe for a prime sign

Many word processors automatically insert an apostrophe when a prime sign is intended. While they may look similar in some fonts, they are different Unicode characters.

Incorrect	Correct
5’ end	5′ end
f’ (x)	f′(x)
45° 30’	45° 30′
6’ 2”	6′ 2″

Likewise, do not use the prime sign where an apostrophe is required.

Incorrect	Correct
the researcher’s data	the researcher’s data
the patient’s symptoms	the patient’s symptoms
It’s important	it’s important

How to insert the prime sign

Most equation editors and scientific writing software include the prime sign as a mathematical symbol. In Microsoft Word, you can insert it through Insert → Symbol or by typing 2032 and pressing Alt + X (Windows). In LaTeX, use the apostrophe character in math mode (for example, f'(x)), which is rendered as a proper prime symbol.

Best practice

• Use the apostrophe (‘) only for possession and contractions.
• Use the prime sign (′) for mathematical notation, derivatives, angular measurements, molecular biology notation (5′ and 3′), and similar scientific conventions.
• Use the double prime sign (″), not a quotation mark (“), for arcseconds or inches when those symbols are required.
• Check proofs carefully, as automatic formatting or font substitutions can accidentally replace a prime sign with an apostrophe or vice versa.

Quick editing checklist for apostrophe usage

Before submitting your manuscript, check the following:

• □ Is every apostrophe showing possession rather than an incorrect plural?
• □ Have you avoided contractions unless required?
• □ Have you distinguished its from it’s correctly?
• □ Are plural possessives correctly punctuated?
• □ Are possessive pronouns written without apostrophes?
• □ Have you checked discipline-specific terms and journal style?
• □ Are abbreviations pluralized without unnecessary apostrophes?
• □ Are units, symbols, and scientific names free from incorrect apostrophes?

Key takeaways

Rule	Example
Singular possession	the author’s manuscript
Plural possession	the researchers’ data
Irregular plural possession	children’s health
Possessive pronoun	its accuracy
Contraction	it’s important
Avoid contractions in formal writing	do not, cannot
No apostrophes for plurals	tables, figures, assays
No apostrophes in units	10 kg, 5 cm, 20 mL
Prefer formal phrasing	the structure of DNA rather than DNA’s structure

In scientific writing, apostrophes should be used sparingly and purposefully. Most appear in possessive constructions, while contractions are generally avoided. While proofreading your dissertation or research paper, pay attention common confusions, especially its versus it’s. This will help produce manuscripts that are precise, professional, and consistent with academic style.