Sunday, November 27, 2022

Grammar tips/rules for scientific writing

In my roles as supervisor, collaborator, reviewer, and editor, I read many scientific papers in draft (pre-publication) form. When reading, my hope is always to concentrate on the science itself - and how well it is communicated. Sometimes, however, I get stuck on particular grammatical errors and find myself repeating again and again and again various grammar "rules." I provide a listing of them here in hopes that they are picked up, used, and propagated just a bit more than at present.

1. Avoid long, complicated compound sentences. These are often very difficult to follow.

2.     Use “which” and “that” properly. “That” should be used for restrictive clauses (“This is the fish THAT Jack caught.) whereas “which” should be used for nonrestrictive clauses (“This fish, WHICH Jack caught, is a salmon.”) Most people use “which” in many cases where “that” is more appropriate.  

3.     Avoid all use of “there is”, “there was”, “there are”, and “there were”, particularly at the start of sentences. Use of these terms can make the subject of the sentence unclear.

4.     Avoid unnecessary amplification of text. For example, say “sneaky mating is successful” rather than “sneaky mating has been found to be successful”. 

5.     Avoid the use of “while”, except when the intended meaning is “during the time that.” In other contexts, “whereas” or “although” are usually better.

6.     Write out all numbers less than 10 (i.e., one, two), unless the number is followed by a unit, such as m, mg, min, h, etc.

7.     “Data” are plural. That is, you don't say: "the data is", you say "the data are." Datum would be the singular version.

8.     “Between” is used in reference to two things. “Among” is used in reference to more than two things. That is, you study the differences between two populations, but the differences among three populations.

9.     Never use “etc.”

10.  Never use “unique” unless you truly mean “one of a kind.” People often say: “Our system represents a unique opportunity to test the theory that…” Instead, say: “Our system represents an excellent opportunity to test the theory that…” Similarly, never use “ideal” or “perfect” in this same context.

11.  My Mom (a grammar expert of sorts) tells me that only God “creates” things (and she isn’t even religious). So, in short, don't use the term create unless you are invoking God.

12.  Strive for parallelism between related sentences that appear close to each other. As a simple example, use “Low predation sites are characterized by few fish predators. High predation sites are characterized by many fish predators.”, instead of “Low predation sites are characterized by few fish predators. Many fish predators are found at high predation sites.”

13.  Beware of misplaced modifiers. For example, “We measured body depth using calipers.” Body depth does not use calipers, as this sentence implies. Instead, use “We used calipers to measure body depth.” Sometimes it is difficult to avoid misplaced modifiers without otherwise destroying the sentence. In such cases, it is forgivable.

14.  Use the active voice (“We measured body depth.”), rather than the passive voice (“Body depth was measured.”), whenever reasonable and when not explicitly disallowed by a journal. Be careful to not use it too much though. Six sentences in a row, all starting with “we”, are very awkward.

15.  Although many would disagree with me, I believe in the power of punctuation. As one small example, I believe the second last phrase in a list of phrases should have a comma before the “and.” For example, “Speciation can occur by genetic drift, mutation, and natural selection.” rather than “Speciation can occur by genetic drift, mutation and natural selection.” Using the latter often introduces confusion when the phrases themselves are longer and contain “and” within them. The cartoon gives another example:

16.  Always use a single space between sentences. All journals do this anyway, and it makes editing difficult if one person (me) uses single spaces and other people (you) use double spaces.

17.  Try not to use “may” unless you are implying permission. Instead consider “might” or “can”.


  1. Expanding on #5, I often feel the same way about "as" when used in a sense other than "simultaneously", and "since" when used in a sense other than "in the time after". For example, "As we didn't have enough fish traps, we resorted to nets", or "Since we didn't have enough...". Instead, write "Because we didn't have enough...". Otherwise, the reader has to think about the ambiguity of the different senses of the word. In general, think about whether there is more than one way to read a sentence, and if there is (even if the alternate readings make no sense really), try to rewrite to eliminate the ambiguity. As my mother (a professional editor) used to say, "Lead the reader by the nose".

  2. A point I would add, again in the spirit of "lead the reader by the nose", is: use connecting words that express the relationships between thoughts. These are words like "similarly", "however", "yet", "meanwhile", "regardless", "but", and so forth. Punctuation can also play this role; semicolons, as in this sentence, are particularly useful for expressing that one thought follows upon the heels of another. Another useful punctuation mark for this purpose – if not overused! – is the en-dash, "–". I prefer it to the longer em-dash, "—", because I find the en-dash more readable—but this choice might be dictated by the journal's style guide.

  3. Finally, one thing that I think is key in scientific writing is to use the same term for the same concept, consistently. If you write "genetic variation" in one place, "genetic variability" in another, "genetic variance" in a third, and so forth, then the reader is left wondering whether you are deliberately referring to different concepts with those different phrases, or whether you are just using inconsistent terminology. This can be incredibly confusing. In general, it is good not to repeat the same word over and over; vary your vocabulary to avoid being repetitive. Exercise your thesaurus a little. But when it comes to scientific terminology, and particularly for the core scientific concepts that you are referring to over and over, the rule is exactly the opposite: settle on a single term and stick with it.


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