Effective writing is readable — that is, clear, accurate, and concise. When you are writing a paper, try to get your ideas across in such a way that the audience will understand them effortlessly, unambiguously, and rapidly. To this end, strive to write in a straightforward way. There is no need to write about science in unusual, complicated, or overly formal ways in an effort to "sound scientific" or to impress your audience. If you can tell a friend about your work, you are off to a good start.
To construct sentences that reflect your ideas, focus these sentences appropriately. Express one idea per sentence. Use your current topic — that is, what you are writing about — as the grammatical subject of your sentence (see
Verbs: Choosing between active and passive voice). When writing a complex sentence (a sentence that includes several clauses), place the main idea in the main clause rather than a subordinate clause. In particular, focus on the phenomenon at hand, not on the fact that you observed it.
Constructing your sentences logically is a good start, but it may not be enough. To ensure they are readable, make sure your sentences do not tax readers' short-term memory by obliging these readers to remember long pieces of text before knowing what to do with them. In other words, keep together what goes together. Then, work on conciseness: See whether you can replace long phrases with shorter ones or eliminate words without loss of clarity or accuracy.
The following screens cover the drafting process in more detail. Specifically, they discuss how to use verbs effectively and how to take care of your text's mechanics.
Verbs
Shutterstock.
Verbs are for describing actions, states, or occurrences. To give a clause its full strength and keep it short, do not bury the action, state, or occurrence in a noun (typically combined with a weak verb), as in "The catalyst produced a significant increase in conversion rate." Instead write, "The catalyst increased the conversion rate significantly." The examples below show how an action, state, or occurrence can be moved from a noun back to a verb.
Using the right tense
In your scientific paper, use verb tenses (past, present, and future) exactly as you would in ordinary writing. Use the past tense to report what happened in the past: what you did, what someone reported, what happened in an experiment, and so on. Use the present tense to express general truths, such as conclusions (drawn by you or by others) and atemporal facts (including information about what the paper does or covers). Reserve the future tense for perspectives: what you will do in the coming months or years. Typically, most of your sentences will be in the past tense, some will be in the present tense, and very few, if any, will be in the future tense.
Past tense
Work done
We collected blood samples from . . .
Groves et al. determined the growth rate of . . .
Consequently, astronomers decided to rename . . .
Work reported
Jankowsky reported a similar growth rate . . .
In 2009, Chu published an alternative method to . . .
Irarrázaval observed the opposite behavior in . . .
Observations
The mice in Group A developed, on average, twice as much . . .
The number of defects increased sharply . . .
The conversion rate was close to 95% . . .
Present tense
General truths
Microbes in the human gut have a profound influence on . . .
The Reynolds number provides a measure of . . .
Smoking increases the risk of coronary heart disease . . .
Atemporal facts
This paper presents the results of . . .
Section 3.1 explains the difference between . . .
Behbood's 1969 paper provides a framework for . . .
Future tense
Perspectives
In a follow-up experiment, we will study the role of . . .
The influence of temperature will be the object of future research . . .
Note the difference in scope between a statement in the past tense and the same statement in the present tense: "The temperature
increased linearly over time" refers to a specific experiment, whereas "The temperature
increases linearly over time" generalizes the experimental observation, suggesting that the temperature always increases linearly over time in such circumstances.
In complex sentences, you may have to combine two different tenses — for example, "In 1905, Albert Einstein
postulated that the speed of light
is constant . . . . " In this sentence,
postulated refers to something that happened in the past (in 1905) and is therefore in the past tense, whereas
is expresses a general truth and is in the present tense.
Choosing between active and passive voice
In English, verbs can express an action in one of two voices. The active voice focuses on the agent: "John
measured the temperature." (Here, the agent — John — is the grammatical subject of the sentence.) In contrast, the passive voice focuses on the object that is acted upon: "The temperature
was measured by John." (Here, the temperature, not John, is the grammatical subject of the sentence.)
To choose between active and passive voice, consider above all what you are discussing (your topic) and place it in the subject position. For example, should you write "The preprocessor sorts the two arrays" or "The two arrays are sorted by the preprocessor"? If you are discussing the preprocessor, the first sentence is the better option. In contrast, if you are discussing the arrays, the second sentence is better. If you are unsure what you are discussing, consider the surrounding sentences: Are they about the preprocessor or the two arrays?
The desire to be objective in scientific writing has led to an overuse of the passive voice, often accompanied by the exclusion of agents: "The temperature
was measured" (with the verb at the end of the sentence). Admittedly, the agent is often irrelevant: No matter who measured the temperature, we would expect its value to be the same. However, a systematic preference for the passive voice is by no means optimal, for at least two reasons.
For one, sentences written in the passive voice are often less interesting or more difficult to read than those written in the active voice. A verb in the active voice does not require a person as the agent; an inanimate object is often appropriate. For example, the rather uninteresting sentence "The temperature
was measured . . . " may be replaced by the more interesting "The measured temperature of 253°C
suggests a secondary reaction in . . . ." In the second sentence, the subject is still
temperature (so the focus remains the same), but the verb
suggests is in the active voice. Similarly, the hard-to-read sentence "In this section, a discussion of the influence of the recirculating-water temperature on the conversion rate of . . .
is presented" (long subject, verb at the end) can be turned into "This section
discusses the influence of . . . . " The subject is now
section, which is what this sentence is really about, yet the focus on the discussion has been maintained through the active-voice verb
discusses.
As a second argument against a systematic preference for the passive voice, readers sometimes need people to be mentioned. A sentence such as "The temperature
is believed to be the cause for . . . " is ambiguous. Readers will want to know
who believes this — the authors of the paper, or the scientific community as a whole? To clarify the sentence, use the active voice and set the appropriate people as the subject, in either the third or the first person, as in the examples below.
Biologists believe the temperature to be . . .
Keustermans et al. (1997) believe the temperature to be . . .
The authors believe the temperature to be . . .
We believe the temperature to be . . .
Avoiding dangling verb forms
A verb form needs a subject, either expressed or implied. When the verb is in a non-finite form, such as an infinitive (
to do) or a participle (
doing), its subject is implied to be the subject of the clause, or sometimes the closest noun phrase. In such cases, construct your sentences carefully to avoid suggesting nonsense. Consider the following two examples.
To dissect its brain, the affected fly was mounted on a . . .
After aging for 72 hours at 50°C, we observed a shift in . . .
Here, the first sentence implies that the affected fly dissected its own brain, and the second implies that the authors of the paper needed to age for 72 hours at 50°C in order to observe the shift. To restore the intended meaning while keeping the infinitive
to dissect or the participle
aging, change the subject of each sentence as appropriate:
To dissect its brain, we mounted the affected fly on a . . .
After aging for 72 hours at 50°C, the samples exhibited a shift in . . .
Alternatively, you can change or remove the infinitive or participle to restore the intended meaning:
To have its brain dissected, the affected fly was mounted on a . . .
After the samples aged for 72 hours at 50°C, we observed a shift in . . .