How do I implement mechanical conventions?

Although we have mostly you how to write professionally by equipping you with methodological reasoning techniques, we also know that there are some tricky grammatical and formatting details that are easy to slip up on, no matter how advanced your writing technique may be.

This page will guide you through some of the more common of these errors in scientific writing. We suggest that you look through anything you write specifically for these types of mistakes before submitting a final draft. If you know that you tend to struggle with grammar and punctuation often, be sure to read your writing through carefully multiple times and perhaps ask someone else to read through your paper as well, because these details can be easy to miss.

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Numbers and units

Writing numbers

Scientists almost always prefer using numerals (“7”) over words (“seven”), since it is more concise and is also representative of the math involved in scientific work. However, in some instances, using words can be more clear. The following table outlines some good guidelines for when to use words versus numerals according to the ACS. However, keep in mind that each publication or organization has its own style guide, and rules may very course-to-course.

Instance	Numeral or Words?	Example(s)	Exception(s)
For units of time or measure	Numerals	6 min 5 g	If it begins a sentence
Numbers nine or less	Words	four samples	For units of time or measure (e.g. 4 s)
Numbers greater than nine	Numerals	25 samples	If it begins a sentence
Numbers that start a sentence	Words	Twenty-five samples	If it’s part of a chemical name (e.g. 2-Butanol)
In a series containing the number 10 or greater	Numerals	4, 8 and 25 samples	If it begins a sentence
In a series containing a number that starts a sentence and is therefore written in words	Numerals	Four, 8 and 25 samples were taken.

Other things to note:

Avoid using numbers at the beginning of a sentence whenever possible. For example, if you want to start a sentence by saying “2 g of NaOH,” you would have to write out “Two grams of NaOH.” So instead, you should write “NaOH (2 g)” or something similar.
Always use a leading zero when writing decimals (e.g. “0.09,” not “.09”)

Writing units

Thankfully, writing units is a little more straightforward than writing numbers. Plus, the conventions are fairly consistent across disciplines. Here are some guidelines for abbreviating (e.g. “g” for “grams”) and writing units in your text:

Guideline

Incorrect

Correct

Abbreviate when following a numeral

5 seconds

25.2 milligrams per liter

5 s

25.2 mg/L

Don’t abbreviate when following a number that is fully written out

Five mg

several s

five milligrams

several seconds

Do not add a period to abbreviations

min.

min

Do not add an “s” to abbreviations

20 mLs

14.3 Pa’s

20 mL

14.3 Pa

Use a slash, not “per,” when using derived quantities

μg per mL

m per s

μg/mL

m/s

In a span of numbers of at least three, only write the unit once*
* If the span includes a modifier, or if “from” or “between” is used to indicate the span, use “to” or “through” instead of an en dash. For example, write “-3 to 4 ˚C” instead of “-3–4 ˚C” and write “from 5 to 10 A/m” instead of “from 5–10 A/m”

3 mL–8 mL

1 m³–11 m³

3–8 mL

1–11 m³

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Mec-1: Test yourself

Correct the mistakes, if there are any, in the way that the numbers and units are written in the following statements.

The ball traveled .35 m per s across the table.
The rock formation originated 3.2 Ga. ago.
6, 8, and 10 measurements were taken, respectively.
Two hundred micrograms per milliliter of zeocin was used to culture the cells.
The experiment was repeated 7 times.
Basalt samples had errors of 0.08 Ma–0.13 Ma.
2’5′-ADP Sepharose was used in the column purification.
Sixteen K was found to be the minimum allowable temperature.
Tests were conducted from 200 to 300 meV.

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Solutions

The ball traveled 0.35 m/s across the table.
The rock formation originated 3.2 Ga ago. (Ga is a unit of time, so 3.2 is not written out.)
Six, 8, and 10 measurements were taken, respectively.
Although this is technically correct, writing the whole number and unit out should be avoided by writing something like the following: “The cells were cultured in zeocin (200 μg/mL).”
The experiment was repeated seven times.
Basalt samples had errors of 0.08–0.13 Ma.
This statement is written correctly, but starting the sentence with a number should still be avoided.
Sixteen Kelvin was found to be the minimum allowable temperature. This statement would be even better and more concise if it was rearranged to say: “The minimum allowable temperature was found to be 16 K.”
Correct.

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Spacing, punctuation, and capitalization

Although it may seem like a small thing, it is important that you correctly punctuate your writing so that it looks professional. The following are some easily confused aspects of punctuation:

Type of Mark	Explanation	Incorrect	Correct
hyphen/dash	Hyphens are used to link two or more words/numbers into a single concept, especially in forming adjectives. “Em” dashes are the width of the letter “m” and can be used like parentheses—to set off one thought from another.^† “En” dashes are the width of the letter “n” and are used to indicate ranges.^†	Of the various geophysical methods-seismic, thermal, electrical, and potential field-seismological data and heat flow studies reveal the most about the composition of the crust (adapted from Rudnick and Fountain 1995).	Of the various geophysical methods—seismic, thermal, electrical, and potential field—seismological data and heat flow studies reveal the most about the composition of the crust. (em dashes) Electrolyte-as-cathode glow discharge atomic-emission spectrometry has been used for the determination of trace metals. (hyphens) The limits of detection were obtained as 0.001–0.08 mg/L. (en dash)
colon/semicolon	Colons (:) come at the end of a full statement only. After the colon comes an example or something else that relates to the previous statement. Semicolons (;) connect two independent statements. The statements should be closely related to one another but should not be additionally connected by “and” or “but.” Semicolons can also be used to add clarity by separating items in a series when the items themselves contain commas.	Scientific discovery has many attributes, including: it is fun, challenging, and fulfilling. Performing controlled science experiments is a great exercise for middle school students; but it is critical that teachers are mindful of safety precautions.	Scientific discovery has many attributes: it is fun, challenging, and fulfilling. Performing controlled science experiments is a great exercise for middle school students; the hands-on experience allows them to learn far more than they would from a textbook alone.
plural acronyms and abbreviations	Add an s, not an ‘s, to the end of an acronym to make it plural.	Microbes produce EPS’s in high quantities.	Microbes produce EPSs in high quantities.

^† To create an em dash in Word, type word(hyphen)(hyphen)word(space); to create an en dash, type word(space)hyphen(space)word(space) and be sure to get rid of the spaces after Word auto-formats the dash.

When you first start writing, you might also struggle with knowing which letters of certain terms should be capitalized and when. Below we provide a summary list with examples of when to use upper- or lower-case letters.

Instance	Letter case	Example(s)
Molecular formulas	Upper for the first letter of each element	NH₄, CuSO₄, Pb²⁺
Binomial nomenclature	Upper for the genus, lower for the species	Twelve strains of Escherichia coli were cultured in LB broth.
Units of measure written in words	Lower, even when derived from proper names	Nerve compression resulted in three-tesla metrics.
Major bodies of land and water	Upper	Gulf of Mexico
Names of molecules, compounds, and solvents	Lower (except at beginning of a sentence).	2,3-Dibromo-1-propanol (98%) was obtained from Aldrich. An precipitate flotation process purified cesium oxide from the mixture.
Particle names	Lower, even when derived from proper names	quarks, bosons
General directions	Lower	eastern Greenland, offshore Alaska
Geometric isomerism	Lower, even at the beginning of a sentence	cis-2-Butene showed a synergystic effect on surface morphology.
Absolute configuration	Upper	The major product was (R)-lactic acid.
Optical isomerism	Upper	All strains did not assimilate D-maltose.
Substituent configuration	Lower, even at the beginning of a sentence	The reaction exhibitied 81% selectivity for m-phenylenediamine.
Theories	Lower	Einstein’s theory of relativity
General geologic formations	Lower*	basin, Nile delta
Seasons of the year	Lower	Samples were collected in the fall of 2015.

^* There are 2 exceptions to this rule: the Permian Basin and Overthrust Belt (according to “Geography and Geology Capitalization” 2015).

Knowing where to put spaces between numbers, symbols, and units can also be tricky. Here is a summary list of some do’s and don’ts for spacing:

Do put a space…

Don’t put a space…

Between numbers and units. Examples: 60 A/s, 20 K, 160 ˚C (“˚C” is a unit, so the space should still come between the number and the unit, not 2 parts of the unit! )

Between initials in your references section. Example: Robbins, C. F.
.
Between a symbol and two numbers around it. Example: 80 ± 2%
.
Between a symbol and a number and a variable around it. Example: p < 0.05

Between numbers and the percent symbol (%). Examples: 42%,
0.3–0.7%
.
Between a symbol and one number. Examples: <20%, -3 K.

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Mec-2: Test yourself

Correct the mistakes, if there are any, in the way that the following statements are punctuated, spaced, and/or capitalized.

The reaction was conducted at 98˚ C.
There was a significant decrease in the amount of denaturation when the temperature was decreased from 65 to 55 ˚C (p <0.01).
QND’s were performed in the non-resonant condition.
The Second Law of Thermodynamics states that the entropy of an isolated system increases over time.
From the lorentzian line the photon decay rate of the resonator was determined as κ/2π=0.8 MHz.
The observed decrease of the cathode fall with decreasing pH was explained by a model that uses two different electron emission processes near the electrolyte cathode, specifically: an emission coupled with hydrated electrons is prominent below pH 2.5 while a proton independent emission of poor efficiency operates above 3 (adapted from Mottaleb, Woo, and Kim 2001).
trans-2,3-dibromo-2-butene (0.2 g) was slowly added to the mixture.
The charging energy was determined as E_C = 5.2 (±0.1) GHz.
Heat–producing elements are elements that generate heat as a results of their rapid radioactive decay (adapted from Rudnick and Fountain 1995).

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Solutions

The reaction was conducted at 98 ˚C.
There was a significant decrease in the amount of denaturation when the temperature was decreased from 65 to 55 ˚C (p < 0.01).
QNDs were performed in the non-resonant condition.
The second law of thermodynamics states that the entropy of an isolated system increases over time.
From the lorentzian line the photon decay rate of the resonator was determined as κ/2π = 0.8 MHz.
The observed decrease of the cathode fall with decreasing pH was explained by a model that uses two different electron emission processes near the electrolyte cathode: an emission coupled with hydrated electrons is prominent below pH 2.5 while a proton independent emission of poor efficiency operates above 3. (While one could argue that a semicolon is appropriate, the makes a colon the better choice.)
trans-2,3-Dibromo-2-butene
Correct.
Heat-producing elements are elements that generate heat as a results of their rapid radioactive decay.

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Tricky words and plurals

Many words that we use in everyday language and frequently in scientific writing sound similar but have very different meanings. To help you keep these words straight so that your writing is as professional as possible, the following table outlines the main differences between some commonly confused words.

Words	Difference	Incorrect usage	Correct usage
Aerial/areal	Aerial refers to being of or in the air; areal has to do with the area of something.	An areal view	An aerial view
Affect/effect	Affect is a verb; effect is a noun.	It significantly effected the results.	It had a significant effect on the results.
Between/among	Between should be used for choices that involve two items; among should be used for choices that involve more. However, “between” can also be used for longer lists if the choices are distinct.	She chose between the NESCAC schools.	She chose among the NESCAC schools. She chose between Middlebury, Bowdoin, and Amherst.
Comprise/compose	Comprise means “to contain;” compose means “to make up.” A larger thing contains or comprises its parts; smaller items make up or compose the larger item.	A series of deep crystal structures comprise the local plateau.	A series of deep crystal structures compose the local plateau. The local plateau comprises a series of deep crystal structures.
Farther/further	Farther applies to physical distance; further refers to figurative distance.	The plasma became unstable further from the membrane.	The method was further developed by our lab.
Fewer/less	Fewer describes distinct, countable quantities; less describes a change in amount.	There were less colonies on the plates containing ampicillin.	There were fewer samples in the second trial. There was less volume in the second sample.
Geologic/geological	Something geologic is a natural phenomenon; if it is geological, it is made by man.	The geological history of the Andes is complex.	The geological map depicts geologic phenomena.
Imply/infer	If it’s implied, then it has been suggested without being explicitly stated; if it’s inferred, it’s been concluded from evidence.	I meant to infer that you were incorrect.	I meant to imply that you were incorrect.
Its/it’s	Its describes possession; it’s is a contraction of “it is.”	Its a simple mistake.	It’s a simple mistake.
Lie/lay	To lie is to rest somewhere; to lay is to actively put something in a place.	He decided to lay down for a nap.	He laid the slide on the bench.
Precede/proceed	The two words have similar, but not identical, meanings. Precede means “to go before;” proceed means “to continue.”	The lab work proceeded the analyses.	The lab work preceded the analyses. The lab work proceeded once funding was renewed.
Presently/currently	Presently means “in the near future;” currently means “now.”	Presently, we are eating dinner.	The food will be ready presently.
Principle/principal	Principle is a noun that refers to a fundamental law or doctrine; principal can be a noun that refers to the chief of something or an adjective meaning “the highest in rank.”	Scientists adhere to many logical principals.	Scientists adhere to many logical principles. His idea was considered principal.
Since/because	Use since to refer to the passage of time; because should be used to show causation.	Since the mixture began to boil, a precipitate formed in the bottom of the flask. (Ambiguous if boiling caused the precipitate or preceded the precipitate.)	Because the mixture began to boil, a precipitate formed in the bottom of the flask.
Surficial/superficial	Surficial should be used to refer to something at the surface; superficial should be used to mean “trivial.”	A superficial geologic deposit was discovered.	A surficial geologic deposit was discovered that had superficial similarities to another nearby deposit.
Then/than	Then is mainly an adverb that indicates time; than is used for comparisons.	The relative binding affinities are less then 0.003.	If the enzyme is cleaved, then the relative binding affinities are less than 0.003.
Vary/range	To vary means “to change;” to range means to “have differences” within limits.	The rocks varied in color from brown to red.	We varied the color of the rocks we showed her.
Which/that	Which is used to provide additional, non-essential information to a statement and should be set off from the main clause by a comma or commas; that is used to clarify or restrict information with further specificity.	The house which I used to live in was sold today.	The house, which I used to live in, was sold today. The house that I used to live in was sold today.
While/although	While primarily means “during the time that” but can be a synonym for “although;” although means “in spite of the fact that.” For clarity, you should avoid using “while” interchangeably with “although.”	While walking down the street can be leisurely, it can be dangerous. (Ambiguous)	Although walking down the street can be leisurely, it can be dangerous. While the reaction was running, he wrote in his notebook.

Students also frequently confuse the singular and plural forms of nouns in science because they are just more accustomed to using one form over the other. When writing, be sure to keep these noun forms straight:

Singular	Plural	Incorrect	Correct
analysis	analyses	Analysis were carried out for synchronization.	The analysis includes five-year means.
bacterium	bacteria	We studied the bacteria for its unusual growth rate.	Whooping cough is caused by the bacterium Bordetella pertussis.
basis	bases	It was confirmed on two basis.	It formed the basis of his intrigue.
criterion	criteria	The first criteria is its visibility.	There was no single criterion for his choice.
datum	data	The data was analyzed.	The data were analyzed. The datum was eliminated.
fungus	fungi (preferred), funguses	The fungi was a vibrant orange color.	Fungi are present in many places we would never expect.
medium	media (preferred), mediums	The media she used was called Lysogeny broth.	She used only a single medium in her experiments.
spectrum	spectra	The spectra shows a deviation at 340 nm.	NMR spectra show small frequency differences.
synthesis	syntheses	Syntheses of ferro-based systems was discussed.	Monomeric syntheses were carried out under the same conditions.
scientific disciplines (physics, mathematics, ballistics, etc.)		Ballistics help us understand projectiles.	Kinetics is the study of bodies in motion. The slow kinetics of the reaction cause particulate to form.
	__ et al.	Soto et al. (2001) has documented variations in trace metal accumulation.	Allen et al. (2011) have shown the mechanism of absorption.
measured quantities, e.g. “75 mA,” “a small amount,” “TSS (total suspended solids)”		TSS (total suspended solids) were measured.	500 years is the time frame usually expected for such movement.

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Mec-3: Test yourself

Do all of the words in the following sentences agree? If not, what word should be changed, and in what way?

The analysis were performed in succession using specialized software.
The lithospheric mantle is the part of the Earth’s mantle which lies immediately under the crust.
The blank spectra was produced side-by-side with the sample spectra, which showed different elements spiked in the tap water.
This data shows a significant decrease in retention with the addition of Compound E.
The LOD values of Hg, Pb, and Cu were improved by more then one order of magnitude.
The phases were marked at less than 1 s.
Ellen et al. (2008) has shown support for this conclusion through work with the human liver.
Coexistence of species at intermediate frequencies of disturbance is thought to require
trade-offs among competitive ability and disturbance tolerance (adapted from Yuan et al. 2000).
A relationship between diversity, genotype, and disturbance frequency was generated in heterogeneous, but not in homogeneous, environments (adapted from Yuan et al. 2000).
In the case of standard electrocatalytic electrodes only formation of hydrogen peroxide was observed, while electrodes additionally modified with graphene can convert oxygen into water via four-electron process.
Surprisingly, while closely spaced, these compounds exhibit the simultaneous oxidation of Fc groups, , indicating a negligible interaction between the organometallic fragments (adapted from Vecchi et al. 2015).
Less final orbits were observed after field gravity stabilization.
The solutions are much less effected by artifacts, such as North–South streaking patterns, than earlier global solutions due to the constraint (adapted from Lemoine et al. 2007).
Electrochemical data for ferrocenyl-containing phthalocyanines and their analogs is summarized in Table 2 (adapted from Vecchi et al. 2015).

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Solutions

The analyses were performed…
…the Earth’s mantle that lies…
The blank spectrum was produced…
…more than one order…
These data show…
Correct
Ellen et al. (2008) have shown…
…trade-offs between competitive ability and disturbance tolerance.
Correct
Correct, although any ambiguity could be solved by using “although” instead.
…although closely spaced… – Using “while” here creates ambiguity and makes the statement sound like the oxidation might only happen when the compounds are closely spaced.
Fewer final orbits…
…are much less affected by artifacts…
Electrochemical data…are summarized in Table 2.

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