In NEC terminology, which word indicates that a rule must be followed?

• A. Shall
• B. May
• C. Could
• D. Should

Answer: (A)

In NEC terminology, certain verbs show how enforceable a statement is. The word that indicates a rule must be followed is a term that marks a mandatory requirement. When you see this word, the action described must be performed for compliance with the code. For example, stating that a conductor or equipment shall be connected or installed a certain way means it is required. If it’s not done, the installation isn’t code-compliant.

Other words convey different levels of allowance or guidance. "May" means permitted or allowed under certain conditions, not mandatory. "Could" isn’t used to express code requirements. "Should" suggests a recommended or best-practice approach, but it isn’t an enforceable obligation.