Expressing Possibility

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Possibility can be expressed in legislation using a variety of words and expressions. Legislative counsel should take care to use a word or an expression that is appropriate to the context, that expresses an appropriate degree of possibility, and that does not create ambiguity about the intended meaning.

Discussion and examples

Possibility can be expressed in legislation using verb forms such as can, could, may and might, and expressions that include the words possible and likely and their variants. These words and expressions should be employed judiciously, as they do not necessarily express the same kind or degree of possibility and could, in certain contexts, lead to ambiguity.


This word expresses possibility in a general sense. The same meaning is conveyed by the expression “it is possible (for X) to”:[1] 

  • if conditions of registration can be established to prevent adverse health impact (i.e., if it is possible to establish conditions of registration)
  • if the pilot can land the aircraft safely (i.e., if it is possible for the pilot to land the aircraft safely)

Because can is also associated with ability, it is especially suitable in cases where “the possibility of an action is due to some skill or capability on the part of the subject referent”,[2] even if the capability is not necessarily desirable:

  • “gas” means natural gas that can be produced from a well (i.e., it is possible to produce the  natural gas)
  • glass that can shatter into sharp or dangerous pieces on impact (i.e., it is possible for the glass to shatter)


This word, which is the past-tense form of can, is used to express possibility in hypothetical situations and to express a weaker or more tentative possibility than can:[3]

  • any situation or condition that the Minister has reasonable grounds to believe could, if left unattended, induce an accident or incident


  • the emergencies that can reasonably be expected to occur at the airport or in its vicinity and that could be a threat to the safety of persons or to the operation of the airport  

    [note the difference in strength between can and could in this example]


This word also denotes possibility, but, unlike can, it is used to describe epistemic possibility, that is, possibility in the sense that the speaker does not know whether the proposition is (or may become) true. It expresses possibility associated with chance [4] rather than with capability. The same meaning is conveyed by the expression “it is possible that”:[5]

  • inspect any books, records, electronic data or other documents that the inspector believes may contain information that is relevant to the inspection (i.e., it is possible that the books, etc., contain information…)
  • disclose to the Minister any actual or potential conflict of interest that may arise and affect their duties (i.e., it is possible that a conflict of interest will arise…)

NB: In legislation may is principally used to grant powers or permission (see the article “Expressing Permission, Powers or Rights”). It is recommended that, to minimize the possibility of ambiguity, legislative counsel avoid using may in cases where more than one interpretation is possible, especially if they have already used the word in its principal legislative meaning in the provision:


This is the past-tense form of may. Like could, it can be used to express possibility in hypothetical situations:

any other element on board the vessel that might, if damaged or used illicitly, pose a risk to people, property or operations

Might can also be used to express a more tentative or weaker possibility than may. (See footnote 3.) Swan actually attempts to quantify the difference between the two words by saying that, in the statement “I may go to London tomorrow”, there is perhaps a 50% chance of the proposition becoming true, while in the statement “Joe might come with me” there is perhaps a 30% chance.[8]


This word is used frequently in legislation:

  • an assessment of the environmental effects that are likely to occur within the area as a result of the proposed activity
  • the symptoms do not indicate a life-threatening condition and the individual is likely to return to their pre-exposure state of health

Dictionaries generally give likely a meaning similar to “probable” or “to be expected”.    A Dictionary of Modern Legal Usage places its strength between possible and probable (it points out that Glanville Williams describes likely as “a strong ‘possible’ but a weak ‘probable’”).[9] It also says that “most often it indicates a degree of probability greater than five on a scale of one to ten”, but cautions that “it may also refer to a degree of possibility that is less than five on that same scale.”[10] Legislative counsel should bear in mind that the degree of possibility or probability conveyed by this word can vary, although they are probably safe in relying on the dictionary definitions.


This word “embraces a wide gamut: everything from the remotest chance to a 100% certainty.”[11] The examples found in legislation suggest, however, that it is used most often to express possibility in the sense of “capability” (“it is possible to”) rather than “chance” (“it is possible that”):[12]

  • a commissioner must, to the extent that it is possible to do so, conduct the examination in the form of oral questions and answers
  • if the survey is conducted in an area where it is possible to sample sediment
  • an aerodrome operator may add a key functionality to a restricted area card only if it is possible to cancel or remove the functionality without damaging or altering any other elements
  • the need to ensure, as far as possible, that at all times the membership will be representative


  • De Wolf, Gaelan Dodds et al. Gage Canadian Dictionary.
  • Fee, Margery and McAlpine, Janice. Oxford Guide to Canadian English Usage. Second Edition.
  • Fowler, H.W. Fowler’s Modern English Usage. Revised Third Edition by R.W. Burchfield.
  • Garner, Bryan A. A Dictionary of Modern Legal Usage. Second Edition.
  • Huddleston, Rodney. English Grammar: An Outline.
  • Huddleston, Rodney and Pullum, Geoffrey K. The Cambridge Grammar of the English Language.
  • Oxford University Press. The Canadian Oxford Dictionary.
  • Oxford University Press. Oxford English Dictionary Online.
  • Quirk, R. et al. A Comprehensive Grammar of the English Language.
  • Shaw, Harry. McGraw-Hill Handbook of English. Fourth Canadian Edition.
  • Swan, Michael. Practical English Usage.


  • [1] Quirk et al., A Comprehensive Grammar of the English Language, p. 222.  “Can” is also used to express ability and informally, instead of “may”, to express permission, but this article is not concerned with those uses. For a discussion of permission, see the article “Expressing Permission, Powers or Rights”.
  • [2] Ibid., p. 222.
  • [3] Quirk (p. 233) states that the tentative note injected by the past-tense form could (and similarly by might in relation to may) is related to the hypothetical use of that form. Both Quirk and Fowler allow that some speakers perceive little or no difference in meaning between the present-tense and past-tense forms; nevertheless, all the grammar and usage sources consulted for this article agree that the past-tense forms of can and may (could and might) convey a weaker, more tentative or more polite idea than the present-tense forms. This is the same sort of distinction that Francophone legislative counsel make between the forms peut and pourrait of the verb pouvoir.    
  • [4] Michael Swan, Practical English Usage (third edition), pp. 316, 320.
  • [5]Quirk, p. 223.
  • [6] Swan, p. 316.
  • [7] Bryan Garner, A Dictionary of Modern Legal Usage, pp. 693 and 694.
  • [8] Ibid., p. 530.
  • [9] Ibid., page 694.
  • [10] The reason for this may simply have to do with ease of use in English sentence structure. “May” and “might” express the idea of chance more concisely and conveniently in many cases. For example, it would be very difficult to substitute  “it is possible that” for “may” in the phrase “any person who the Minister considers may be affected by the order”.