Verb Tenses – Science
Use of the correct verb tense allows you to express clearly the time relationships among your ideas. When deciding which verb tense to use, aim for consistency, simplicity, and clarity. Whenever possible, keep verbs in the same tense (consistency), and use either the simple present or the past tense (simplicity). Above all, choose the verb tense that most clearly expresses the idea you want to convey (clarity). In general, use the present tense to describe actions and states of being that are still true in the present; use the past tense to describe actions or states of being that occurred exclusively in the past.
Below are some discipline-specific guidelines for how to use verb tenses effectively in the sciences. For details on tenses in literature writing, see handout “Verb Tenses—Literature.”
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.
Use past tense to discuss completed studies and experiments:
- We extracted tannins from the leaves by bringing them to a boil in 50% methanol.
- We hypothesized that adults would remember more items than children.
Use past tense when referring to information from outside sources:
- Paine (1966) argued that predators and parasites are more abundant in the tropics than elsewhere.
- Kerr (1993) related the frequency of web-decorating behavior with the presence of birds on different Pacific islands.
Note: a common mistake in science writing is the use of present tense when referring to what other authors have written.
As in writing for other disciplines, use present tense in science writing when describing an idea or fact that is still true in the present:
- Genetic information is encoded in the sequence of nucleotides on DNA.
- Previous research showed that children confuse the source of their memories more often than adults (Lindsey et al. 1991).
Also use present tense in science writing when the idea is the subject of the sentence and the citation remains fully in parentheses:
- Sexual dimorphism in body size is common among butterflies (Singer 1982).
Contrast the above sentence to the following, also correct, construction:
- Singer (1982) stated that sexual dimorphism in body size is common among butterflies.
Use future tense in science writing as you would in any other discipline—to present perspectives on what you will do in the future:
- In a follow-up experiment, we will study the role of ultraviolet light variations in feeding behavior of genus Polyommatus butterflies.
The logic and practice of the discipline for which you write determine verb tense. If you have questions about tense or other writing concerns, check with your professor.