Understanding the linguistic nuances of the modal verb “can” is essential for clear communication, as its usage has evolved significantly since the 19th century. While historically associated strictly with ability, modern English dictionaries confirm that “can” is now widely accepted for granting or requesting permission in both spoken and written contexts.
The Evolution of “Can” in Modern English
The primary function of “can” is to denote ability or capacity. According to the Cambridge Dictionary, it serves as a modal verb to describe what someone is capable of doing, such as “She can speak four languages.” This definition encompasses physical capability, intellectual knowledge, and general possibility.
However, usage has shifted regarding permission. The Merriam-Webster Dictionary notes that using “can” to ask for or grant permission has been common since the 1800s. While some traditionalists historically argued that “may” should be the preferred term for permission, “can” is now firmly established in standard English. The Collins English Dictionary clarifies that “cannot” or “can’t” is similarly used to indicate that someone is not allowed to perform an action.
Common Usage and Idiomatic Expressions
Beyond its standard grammatical role, “can” appears frequently in idiomatic phrases that reflect informal communication styles.
- “Can do”: An informal expression used to indicate that a speaker is willing and able to fulfill a request.
- “No can do”: A colloquial way to express that a request cannot be fulfilled or that an individual will not perform a specific task.
- “Can always”: Often used to suggest a fallback solution or an alternative course of action, such as “we can always leave.”
Distinguishing Ability from Permission
While the lines have blurred in casual conversation, professional writing often benefits from distinguishing between the two intents.
| Usage Category | Primary Meaning | Example |
| :— | :— | :— |
| Ability | Possessing the skill or capacity | “He can calculate the figures.” |
| Permission | Having the authority or allowance | “You can access the secure file.” |
As of June 2026, the consensus among major linguistic authorities remains that “can” is versatile. Whether you are describing a technical capability or granting clearance for a project, the term is universally understood. If you seek to maintain a more formal tone in corporate or legal documentation, you may still choose to use “may” for permission, but “can” is no longer considered incorrect in these scenarios.