Mistook vs. Mistaken
Use “mistook” for the simple past of the verb “mistake” and “mistaken” as its past participle, especially after have/has/had. The guide preserves documented regional or alternate forms rather than treating the pair as an absolute binary.
Use “mistook” for the simple past of the verb “mistake” and “mistaken” as its past participle, especially after have/has/had.
Key details
Choose the right form
| Meaning / situation | Form / construction | Decision |
|---|---|---|
| simple past of the verb mistake | mistook | Use “mistook.” |
| past participle after have/has/had or in a passive/perfect construction | mistaken | Use “mistaken.” |
| adjectival sense meaning wrong in a belief or judgment | mistaken | “Mistaken” can also function adjectivally. |
Quick tests
Meaning / construction test
Do you need the simple-past verb form with no perfect auxiliary?
If yes: Use “mistook.”
If no: Use “mistaken” for the past participle, and recognize its separate adjectival use when the sentence describes someone as wrong.
Caveat: “Mistaken” is not only a participle; it also has an adjectival use, so decide from the sentence role rather than from tense alone.
Examples
I mistook the side entrance for the main door.
“Mistook” is the simple past of “mistake.”
I have mistaken this code for the previous version before.
“Mistaken” is the past participle after “have.”
I was mistaken about the meeting time.
“Mistaken” is used adjectivally here.
Usage notes
This guide addresses the verb paradigm; “mistaken” can also be used adjectivally.
Further guidance
Core difference
“Mistook” is the simple-past form of the verb “mistake”; “mistaken” is the past participle and can also function adjectivally in other contexts.
Fast Test
For a standalone finite past-tense use of the verb, choose “mistook.” After have/has/had, choose “mistaken.”
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Mistake — Cambridge Dictionary (opens in a new tab)Cambridge University Press · Direct verb-form evidence for mistake, mistook, mistaken.