What this handout is about

Modal verbs (must, will, would, should, may, can, could, might, must) precede another verb. Modals do not have subject-verb agreement or take the infinitive “to” before the next verb.

This handout shows how modals in academic writing can change a sentence’s meaning into a prediction, suggestion, or a question. Modals can also serve a social function to show uncertainty or politeness. They are especially common in discussion sections of research papers.

How to use this handout

This handout is best used with a piece of writing that benefits from being subjective. Each function alters a sentence’s perspective differently.

Logical possibility: expresses a degree of probability

  • Before: This is the fastest way to drive to Westwood.
  • After: This might be the fastest way to drive to Westwood.

Ability: shows capability

  • Before: Riding the bus avoids traffic.
  • After: Riding the bus can avoid traffic.

Necessity: expresses directness in attitude

  • Before: Wash your hands before preparing food.
  • After: You wash your hands before preparing food.

Permission: shows politeness

  • Before: I am going to your office hours.
  • After: Can I go to your office hours?

Strength and Frequency of Modal Verbs

In academic writing, modal verbs are most frequently used to indicate logical possibility and least frequently used to indicate permission. The nine modal verbs are listed under each of the functions they can perform, and are ordered from strongest to weakest for each function. Notice that the same modal can have different strengths when it’s used for different functions (e.g., may or can).

Most frequent Least frequent


Logical possibility Ability Necessity Permission
must can must may
will/would could should (as advice) could
should can

Functions of Modal Verbs

This second table organizes examples of each modal by its use, also including an explanation.

Use Explanation of use Modals Examples
Logical possibility This use of modals hedges, or weakens, the certainty of a sentence. The stronger the modal, the stronger the possibility. Must is so strong that it is almost forcing something to happen. On the opposite end, can, could, and might are all equally weak and show a lack of commitment or confidence.

Strongest logical possibility = most probable (but still not guaranteed)








Those clouds must mean that it will rain later.

As a result, the market will close earlier than usual today.

This naïve approach would not work well everyday.

Careful thought should be put into important decisions.

This may ultimately lead to better outcomes.

Careless actions can lead to disastrous results.

Changing these settings could produce more favorable results.

These factors might contribute to the success of the project.

Ability This use shows ability, which is binary, rather than possibility, which falls on a spectrum.

Strongest ability = most direct

cancould The literature can be organized by date, author, or argument.
A person who could interpret the results assisted the researcher.
Necessity This use gives advice or makes a recommendation.

Strongest necessity = most direct

mustshould A closer examination reveals that the subject must be treated with great care.
Our findings suggest that health care providers should strive to be sensitive to the needs of their patients.

This use asks or gives permission in the form of a question. It almost never appears in published academic writing, but frequently appears in academic correspondence such as e-mails, proposals, or revisions. The strongest modal in this use, may, is the most polite and indirect, whereas can is the more direct and slightly impolite.
Strongest permission = most polite


May I request a copy of the article that you published in 1999?

Could you get back to me by Tuesday?

Can you elaborate on the significance or contribution of this?

Works consulted

We consulted these works while writing the original version of this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find the latest publications on this topic. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial.

Celce-Murcia, Marianne and Diane Larsen-Freeman. The Grammar Book: An ESL/EFL Teacher’s Course. 2nd edition. Boston: Heinle & Heinle, 1999.

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