Some of the most basic sentence structures can result in clear scientific writing.

Many students learn the basics of grammar early in their academic careers, but may not subsequently re-visit the basic components of writing. However, using simple sentence structures can help to clarify scientific writing. Some recommendations for clear writing grounded in the basics of English grammar are:

1) Use a simple sentence structure with a central verb.

2) Use verbs that are clearly members of one of the three basic verb types.

3) Use active voice to make sentences as short and straightforward as possible.

1) Use a simple sentence structure with a central verb.

One goal of scientific writing is to express ideas using the fewest, simplest words possible. Effective sentences are concise and express ONE main idea per sentence. Therefore, using the simplest sentence structure possible will help clarify scientific writing. Several principles can contribute to simplifying sentence structure.

A) A Subject - Verb - Object sentence structure is sufficient for most scientific sentences.

One of the simplest sentence structures in English is:

SUBJECT - VERB - OBJECT (SVO structure).

In the SVO structure, the verb is central to the sentence and connects the subject and the object. For example, in the sentence "Heart disease is the leading cause of death in the United States,"  "Heart disease" is the subject, "is" is the verb, and "leading cause of death in the United States" is the object. 

The SVO structure is a fundamental part of the English language. Scientific writing seldom requires sentence constructions more complex than SVO (e.g. scientific writing does not commonly require intransitive constructions). Therefore, deliberately selecting a SVO structure is a reasonable approach to clear scientific writing.

B) The Subject, Verb, and Object are clearest when as close together as possible.

Having the Subject, Verb, and Object of a sentence as close together as possible improves the clarity of the sentence (Gopen and Swan, 1990). A useful strategy for writing sentences is to start with the KERNEL (central core) of the sentence. Only AFTER creating a clear kernel, add modifiers that put the sentence into context.

For example, a group of students wrote the sentence "Due to this fact, we hypothesized that our unskilled athletes, although dependent on the relationship between muscle activation and interaction torque of the wrist, elbow, and shoulder, will ultimately rely more on the interaction torques in the wrist, elbow, and shoulder and less on the muscle activation of the wrist, elbow, and shoulder to produce a higher velocity baseball throw." How could we improve the sentence?

The Kernel (central point) of the sentence is: "We hypothesized that unskilled athletes will rely on interaction torques more than muscle torques." Therefore, it would be clearest to begin the sentence with the central point. Adding modifiers at the END of the sentence can provide context:

"We hypothesized that unskilled athletes will rely on interaction torques more than muscle torques during high-velocity baseball throws at the wrist, elbow, and shoulder joints."

C) Limit sentences to ONE or fewer commas per sentence.

Commas can be helpful to distinguish between transitions and premises. Commas can also delimit lists, where individual elements of the list may be separated by commas. However, commas can also create sentences that express more than one idea or overly-complicate the sentence by separating the subject, verb, and object. Therefore, use at most ONE comma per sentence unless there is a compelling reason to use more.

D) Repetition can help clarify writing and help audiences focus on content.


Repetition can reduce the effort that audiences must devote to understanding structure, and therefore help audiences focus on content. Therefore, repeating the SVO structure is one way to simplify scientific writing. 

If repetition results in text that does not sufficiently flow, flow can be improved in revision. Starting from a simple, repeated framework will help the revised text maintain clarity and accuracy.

APPLICATION: The SVO structure can help ensure that every sentence has a clear and unambiguous subject, a central verb, and a clear and unambiguous object. Subject, Verb, and Object should be as close together as possible in the sentence. One useful method of revision is to identify the subject, verb, and object of each sentence in a paper. If any component is missing or unclear, then the sentence may need revision.

2) Use central verbs that are clearly members of one of the three basic verb types.

One way to group central verbs is into three main types:

1) Being verbs.

2) Action verbs.

3) Linking verbs.

1) Being verbs. The verb "To Be" is arguably the simplest verb in English, and is also the primary being verb. When possible, use the simple verb "To Be," even if using "To Be" results in repetitive sentences. Other being verbs (e.g. "seems," "becomes," etc.) are vague and confusing if used unnecessarily.

2) Action Verbs. In contrast to being verbs, there are many action verbs. Action verbs typically involve a subject doing something to an object. For example, "we measured length with a digital caliper" uses the action verb "to measure" to connect the subject "we" with the object "length" with the indirect object of the specific method of measuring length. Similarly, "smoking causes cancer" uses the action verb "to cause" to connect smoking to cancer. Causal relationships require particular care on the part of the author to clearly and unambiguously establish subjects and objects.

3) Linking Verbs. Linking verbs provide the opportunity for important nuance in scientific writing. Technically, "to be" and other being verbs are also linking verbs. However, the nuance of linking verbs other than "to be" require care to ensure that they are used correctly. Linking verbs connect subjects and objects (or attributes) in a variety of different ways. Some of the more common linking relationships in scientific writing are:

"X is associated with Y." The verb phrase "is associated" links X and Y, but does NOT argue that the relationship is causal, coincidental, etc. Moreover, simply finding an association does not specify the type of association (e.g. linear, logarithmic, exponential, etc.). Association is useful if a clear relationship between two things exists, but the nature of the relationship is unknown.

"X is correlated with Y." Correlations are essential for experimental science. Therefore stating that there is a correlation between two things means something: that you (or someone else) have performed the mathematical steps required to establish a correlation and determine its strength and statistical significance. Therefore, stating that there is a "correlation" is a much stronger statement than simply asserting that there is an "association."

4) A fourth verb type, "helping verbs," can ensure that scientific statements have the appropriate scope. However, as suggested by their name, "helping" verbs work with the central verb to help provide specificity or context. Therefore, helping verbs have not been included in the main verb types. We will review "helping" verbs more when discussing specificity.

APPLICATION:  Clear sentences contain central verbs that can be clearly identified as one of the three main verb types. If a sentence is confusing, check to make sure that the verb is clear and central to the sentence.

3) Use active voice to make sentences as short and straightforward as possible.

Passive voice can be useful for writing when the "agent" of writing is unimportant or useful to remain undefined (Knight, 2003). Passive voice can be appropriate for some situations. For example, passive voice may be useful when offering recommendations where the target audience is unknown (such as the current document). 

Some scientists and educators argue that using the passive voice helps make scientific writing more "objective" (Leather, 1996). For example, a passive construction for a hypothesis could read "It was hypothesized that...," whereas an active construction would read "We hypothesized that..." However using passive voice to affect objectivity has the potential to create an unnecessary fiction: that science is more objective than it is. Although, being as objective as possible is an important goal, science is a human process and cannot be completely objective. Moreover, the premise that writing with language that seems objective makes science more objective is a non-sequitur. The appearance of objectivity does not affect the actual objectivity of the research.

The most important goal for communicating science is not objectivity, but clarity and fidelity to the procedures and outcomes being explained. Therefore, if an author or authors performed an experiment and analyzed data, the most straightforward and faithful representation of the experimental process is one where the author(s) are the agents of the writing. Therefore, active voice is most appropriate for many aspects of scientific papers.

For example, if you performed extensive research on a topic and developed a testable hypothesis, then the most faithful representation of that process is an active construction: "I hypothesized that..." There is no reason to obscure agency because the agent is known: it is you. Pretending that the hypothesis somehow spontaneously generated is disingenuous.

Likewise, if you made a measurement, the most faithful description of the process is using the active voice ("I measured X...). If you have multiple authors of your paper, then all authors take responsibility for all aspects of the paper. Therefore, if the paper involves a measurement, write "We measured X..." If the authors agree on a conclusion, the appropriate explanation of the conclusion would be active: "We conclude that..." Etc.

Active voice has other virtues that have convinced authorities on writing to recommend active voice for over a century (Strunk and White, 2000). For example, active voice typically uses fewer words than passive voice. For example, a passive construction might read: 

"Significant improvements to balance scores were observed after treadmill training” (10 words). The passive construction needlessly obscures the subject. 

An active construction might read:

"Balance scores improved significantly after treadmill training” (7 words)." Not only does using active voice make the subject clearer, but reduces the word count by 30%. 30% is a substantial reduction in words.

Not all sentences that use active voice are equally strong. For example, which sentence is best?

1. "It was observed that Group A had a significantly higher average score than Group B” (passive voice; 13 words).

2. "We observed that Group A had a significantly higher average score than Group B” (active voice; 12 words).

3. "Group A had a significantly higher average score than Group B” (active voice; 9 words).

Sentence (3) is clearest. Beginning with a specific subject helps keep the focus on the CONCLUSIONS of each sentence (instead of less relevant and distracting subjects such as you as the authors, or indeterminate observers). The sentence could be followed by an explanation of why the score difference is important, etc. 

Active voice is often more straightforward and specific than passive voice. Active voice typically reduces the amount of text needed to support an idea relative to passive voice. Active voice is more faithful to the process of science (more "truthful") than passive voice. Therefore, clear scientific writing uses active voice unless there is a specific reason to use passive voice

APPLICATION. Use active voice unless there is a specific reason to use passive voice. If a sentence is confusing and uses passive voice, consider revising the sentence to active voice with a clearly-defined subject.