Modal Verbs

Introduction

Modal verbs, such as “Must”, “Should”, “Can” and “Will”, express necessity, recommendation, capability, or certainty. Some modal verbs have multiple meanings, which can lead to ambiguity if not used precisely. This chapter provides guidelines for selecting and using modal verbs effectively in technical writing.

Common Modal Verbs

The following modal verbs are commonly used in technical writing:

Modal Verb	Function
Must	Indicates a mandatory action.
Should	Represents recommendations or best practices.
Can	Describes ability or general possibility.
Will	Indicates a definite future action or a guaranteed outcome. (Prefer present tense when possible for conciseness. See Future Tense for more details.)

Note

Avoid using “Shall”, “May”, “Might”, “Could”, and “Would” due to ambiguity. See Avoid Ambiguous Modal Verbs for details.

Effective Use of Modal Verbs

Choose Precise Modal Verbs

Select modal verbs that precisely convey the intended level of obligation, possibility, or certainty.

Intent	Modal Verb	Example
Mandatory Requirement	Must	The interval between two consecutive pulses must be greater than one ETM clock cycle. The divider must not be configured to 1.
Recommended Practice	Should	A copy of this key should be kept by any party who needs to verify the device. This option should not be enabled for applications with high security requirements.
Ability or General Possibility	Can	This bit can only be written by the debugger. Users cannot directly access the eFuse memory.
Definitive Future Action	Will	Access to entries marked as invalid memory types will result in fetch fault. The data will not be shared with third-party vendors without explicit consent.

Frequent Misuse Patterns of Key Modal Verbs:

• Misusing “Should” for Mandatory Actions

  “Should” is often misused to express mandatory actions, leading to ambiguity about the level of compliance required. Use “Must” to clearly indicate the requirement, or use the imperative mood for instructions.

  Less Precise	More Precise
  Users should make sure the key to be used has been burned in eFuse.	The key must be burned into eFuse before use.
  Only documented patterns should be used.	Use only documented patterns.

• Misusing “Can” for Recommendations

  “Can” is often misused to suggest recommendations, implying possibility instead of necessity. Use “Should” to clearly indicate recommended actions.

  Less Precise	More Precise
  You can enable flash encryption in the “Release” mode for production use.	You Should enable flash encryption in the “Release” mode for production use.

Avoid Ambiguous Modal Verbs

Avoid modal verbs like “Shall”, “May”, “Might”, “Could”, and “Would”, as they can confuse the intended level of certainty or obligation. Instead, replace them with explicit language or more definite modal verbs like “Must”, “Should”, or “Can”.

Avoid	Preferred	Comment
The user shall install the required drivers before proceeding.	The user must install the required drivers before proceeding.	“Shall” is ambiguous, implying either a command or suggestion; “Must” clearly indicates an obligation.
The device may transmit data over Wi-Fi.	The device can transmit data over Wi-Fi.	“May” implies uncertainty; “Can” clarifies technical capability.
The module may fail to initialize if the input voltage is unstable.	The module fails to initialize if the input voltage fluctuates beyond 5%.	Using present tense with a specific technical condition improves clarity.
Users may edit system settings.	Users have permission to edit system settings.	“May” is ambiguous; explicit permission removes confusion.
The system might overheat.	The system can overheat if ambient temperatures exceed 40 °C.	“Might” is vague; “Can” clarifies the possibility under a condition.
Incorrect configurations could lead to data loss.	Incorrect configurations can lead to data loss.	“Could” is tentative; “Can” states a clear possibility.
The system would fail to start if the configuration file is missing.	The system fails to start if the configuration file is missing.	Direct condition without “Would” avoids unnecessary hypothetical phrasing.

Rules for Replacing Ambiguous Modal Verbs:

• Avoid “Shall”: use “Must” (for requirements) or “Should” (for recommendations).

• Avoid “May”: use “Can”, present tense or explicit permission phrases.

• Avoid “Might” and “Could”: use “Can” or present tense with conditions.

• Avoid “Would”: use present tense.

Reduce Unnecessary Modal Verbs

Overusing modal verbs introduces unnecessary complexity and reduces clarity. Use direct statements or the imperative mood for conciseness.

Example

Overuse	Concise
The service will automatically restart after a crash.	The service restarts automatically after a crash.
You should be able to access the database after logging in.	Log in to access the database.
ULP-FSM can be stopped by running HALT instruction.	To stop ULP-FSM, run the HALT instruction.

By selecting the appropriate modal verbs, avoiding ambiguous phrasing, and minimizing unnecessary usage, technical documentation becomes clearer and more actionable.

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