Which term denotes an error produced when a learner is tired and knows the rule but fails to apply it?

• A. Mistake/slip
• B. Global error
• C. Post-systemic error
• D. Multi-word units

Answer: (A)

When a learner already knows the rule but doesn’t apply it in the moment because of tiredness or distraction, the error is a slip—a performance error. Slips show up in real-time production: the knowledge is correct, but execution falters due to processing limits or momentary lapse. For example, if the rule says to add -s for third-person singular present and the speaker says “She walk to the store” after a long day, that incorrect form comes from a slip, not a gap in knowledge.

This is different from a mistake rooted in lack of knowledge or a general misunderstanding of the form, and it isn’t about broader, global failures of the sentence, post-systemic issues, or collocations. So the best term for this scenario is a slip.