There has been a recent push toward developing programs and workshops focused on improving writing skills for scientists. Science writing is crucial within the research community, refining these skills is necessary.

In this article, we highlight a few grammatical rules and scientific writing standards from several resources including the ACS guide, the AP Stylebook, the Holt Handbook, the NCBI style guide and the AMA handbook.

science writing handbook download for free

General English rules:

A vs. An:

Most people know the basic rule: If the word that follows begins with a vowel, you use an. Yes, that’s true in most cases, but the mistake occurs when people don’t realize that there are special exceptions to the rule.

For instance, if the word that follows begins with a consonant that sounds like a vowel, the writer should use an. But the bigger mistake observed is when the word that follows begins with a long U. Because the long U has the sound of a consonant (YOU), the writer should use a.

A vs. An examples of right vs. wrong - scientific writing mistakes

*Remember, the purpose for the A vs. An rules is to promote a flow of easy communication. When in doubt, do what would sound better to the reader.

As vs. Because:

Sometimes, people use the word as in place of because. Using as does sound more professional, but it’s technically incorrect

According to the NCBI style guide, a writer should never use as when the word because should or could be used.

Incorrect Example:

The polyA tail of an mRNA (cDNA) sequence should never be trimmed as it provides a useful landmark.

Correct Example:

The polyA tail of an mRNA (cDNA) sequence should never be trimmed because it provides a useful landmark.

General scientific writing standards:

Preventive vs. Preventative:

This is a situation where an English variation of two words exist, and people commonly say phrases such as preventative medicine. And if we often speak it, we often write it. However, the AMA handbook has stated that the proper variation in medical and scientific writing is always preventive.

Bacteria vs. Bacterium/Data vs. Datum/ Media vs. Medium

So many of the words we use in science are rooted in Latin or Greek. That means the endings that would either make a word plural or singular are going to be different from English.

In these three examples, the word ending in a is plural and the word ending in um is singular.

Plural: bacteria, data, media

Singular: bacterium, datum, medium

Ps. Yes, that means Data from Star Trek (TNG) has a plural name.

Units of Measurements:

The ACS, AMA and NCBI guides have consistent standards on how to write unites of measurement. The guide states that there should always be a space placed between the numeric value and the unit of measurement. There’s a twist in this rule: If you’re dealing with a concentration, then you do not use a space.

Example: 25 g and 100 ml and 0.5M

Names of Chemicals:

According to the ACS handbook, the names of chemicals are not capitalized. Of course, the exception to the rule is if a chemical is a proper noun or named for a person or uses a common name that is an acronym.

This rule is taken to another level when we introduce chemical prefixes such as “ortho,” “cis,” “trans,” “iso,” etc. Never capitalize chemical prefixes, even if they begin a sentence. These prefixes, or descriptors, can be capitalized if they are standing alone at the beginning of a sentence. Also, remember to italicize them.

Correct way of writing chemical directional names - mistakes you might be making on your scientific writing

Cross-Link/ Double-Stranded/ Single-Stranded:

These words, related to DNA and RNA are always hyphenated according to the ACS guide. The ACS handbook also has a page on other scientific words that should be hyphenated.

When in doubt, look up the rule. If you can’t find it, come up with your own and consistently apply it throughout the entire paper.

Gram – as in Gram staining, gram-positive and the Gram’s method:

How you see it in the title is how it should be written.

Gram should never be hyphenated when referring to Gram staining. Also, never apply an apostrophe S in this context.

When referring to whether a bacterium is gram-positive or gram-negative, use a hyphen and do not capitalize the gram.

The only time the apostrophe S should be used is when referring to Gram’s method. Notice, the hyphen is not used in this example.


Keep organelles in their lowercase form. But there are two special cases. The Golgi is always capitalized because it was named for Camillo Golgi, and when abbreviating the endoplasmic reticulum, capitalize the acronym (ER).

Prefixes: Anti, Bi, Co, Ex, Micro, Multi, Pre, Re, Semi, Sub…

The general rule: In most cases do not hyphenate these prefixes. Note: There are certain prefixes that defy the general rule.

Exceptions/Special Cases:

  • Use a hyphen when the first letter of the word that follows should be capitalized.
  • Use a hyphen when the first letter of the word that follows begins with the same letter the prefix ends with (re-engineer).
  • Use a hyphen when the combination without a hyphen makes the word unclear to the reader.

Special Cases on an individual basis:

  • Anti: This prefix almost always defies the general rule. When using anti, hyphenate in all cases except in special situations where the word has a meaning of its own.

DO NOT HYPHENATE: Antibiotic, anticlimax, antidepressant, antidote, antigen, antihistamine, antimatter, antiseptic, antioxidant and antitoxin. When in doubt, look it up.

  • Co: Aside from the general rule, and the special cases listed, you should retain a hyphen when forming nouns, adjectives and verbs that indicate occupation.

Hyphenate occupations: co-author, co-worker, co-owner.

Hyphenate words that might be otherwise confusing to the reader: co-regulate.

Do not hyphenate existing words with co: coexist, coenzyme, copay

  • Non: The general rules apply in this example (do not hyphenate).

Example: nonspecific, noncovalent, nonionic, nondenaturing.

Remember, if the word is long, clunky and becomes harder to read if it isn’t hyphenated, then you should use a hyphen.

  • Pre/Re: Pre and Re are usually never hyphenated. But there are some special cases

Remember to be careful in situations where applying or not applying a hyphen would change the meaning of the word. For example, recover means to regain, not to cover again. In the second case you would use re-cover.

research manuscript writing handbook