Style Guide > 5 Grammar and Style > [5.23] Modal verbs
[5.23] Modal verbs
5.23 Modal verbs
The verbs “will”, “should”, “can”, and “may” are examples of modal verbs. We use them every day without much thought, but when used in the wrong context, they can cause ambiguity and misreading. And some we should avoid altogether.
Modal verbs, although commonly used, are some of the most grammatically complex parts of the language. They are used to modify the strength or mood of other verbs—in some cases, the differences are subtle but important. They are also verbs in their own right or participles of verbs. Furthermore, their negative forms do not always mirror their meanings. Their recommended usage is summarised here and explained, with examples, in the text that follows:
Do not use. Can imply ability or necessity. Use permit (v.).
Do not use. Archaic. Can imply intention. Use require (v.) or comply (v.).
Do not use. Can imply doubt or inability. Use prohibit (v.).
Okay. Can imply discouragement.
5.24 Business vs legal writing
This guide applies to general business and technical writing. Legal writing has its own guidelines, especially regarding “shall”, “should”, and “may”. But just because one of these words is used in legislation or a legal document, it doesn't mean that we should follow their lead. Business and technical writing is all about clarity and mitigating risk—you would hope that was also true about legal writing.
5.25 can, might, and must
If the intended meaning is clearly either “can” (ability), “might” (possibility), or “must” (necessity), then use those precise words because their meanings are always clear—for example, “you can submit”, “you might submit”, or “you must submit” (instead of “you should submit” or “you may submit”).
5.26 should
If the intended meaning is recommendation or encouragement, then use a strong verb, such as “recommend” or “encourage”—for example, “ABC recommends that”. Avoid “should” unless you are certain that the reader will only interpret it as an encouragement or recommendation—for example, “you should consider”, “we should go”, and “When should I use 'should'?”. Often, the writer intends necessity but uses the softer “should” instead of the more direct (and unambiguous) “must”.
5.27 may
If the intended meaning is permission, then use a strong verb, such as “permit” or “allow”. Avoid “may”—it might be misread to mean ability or possibility. Often, “can” or “might” will better (and unambiguously) reflect the writer’s intended meaning.
5.28 will
If the intended meaning is intention, then use a strong verb, such as "intend"—for example, "I intend to submit". Avoid using "will", particularly in the second person, because it can sound like an imperative—for example, "you will submit" and "participants will submit" (it's similar to "shall").
5.29 could
If the intended meaning is potential or uncertainty, then use "could"—for example, "you could submit the application today, but …". There is a difference between "could" and "might" in the sense that "could" indicates that an action can be done but might not, whereas "might" indicates that it is only a possibility. "Could" is also used in polite requests.
5.30 would
If the intended meaning is conditionality, then use "would"—for example, "the results would be different if …". "Would" is also used in polite requests. Do not use for simple future tense unless a condition is specified; instead use “will”.
5.31 shall
"Shall" also suffers, to some extent, from ambiguity, but the main reason we don't use "shall" is because, in the context of an imperative ("the participant shall submit"), it's old-fashioned and is fast disappearing from common use—it's a bit too Old Testament for modern writing, like "shan't". In most cases "must" can be used instead—for example "participants must submit" (meaning the only other choice is to not submit). If the intended meaning is obligation (instead of necessity), then use a strong verb, such as "require" or "mandate"—for example, "participants are required to submit" (meaning there are no other choices). "Shall" does survive in other contexts, but generally only in the first person—for example, "Will you be there? I shall." "Shall we go?"
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