Past Tense of “mistake”
The past tense of mistake is mistook; the past participle is mistaken.
Why “mistake” behaves this way
"Mistake" joins "mis-" to "take," a Norse-derived verb whose Viking-era arrival in English carried along a strong ablaut vowel pattern still visible in "took" and "taken" today, and the prefixed compound simply rides on that same pattern rather than developing any conjugation of its own. The compound itself is first recorded in Middle English, considerably later than the original borrowing, showing that English speakers were still actively building new prefixed verbs on top of relatively recent Norse loanwords well into the medieval period.
The original sense behind "mistake" was closer to "take wrongly" or "take in error," as in physically grabbing the wrong object, before the meaning broadened into its now-dominant abstract sense of holding an incorrect belief or misidentifying something ("I mistook him for his brother") — a shift from concrete, physical error to cognitive, perceptual error. This kind of drift from physical grasping to mental or perceptual error also shows up in other English vocabulary, such as "grasp" itself, which similarly extended from literal handling to intellectual comprehension.
The common confusion
There's no homophone trap, but "mistake" the verb is easily confused in register with "mistake" the noun (an error), which is far more common in everyday speech ("that was a mistake") than the verb form is, leading some learners to underuse the verb even though it's perfectly standard. The phrase "by mistake," a fixed adverbial expression meaning accidentally, uses the noun exclusively and never the verb, another small but genuine source of confusion for learners still sorting out which form belongs where.
How it's actually used
"Mistaken" functions independently as a common adjective describing a person who holds an incorrect belief ("you are mistaken"), a usage at least as frequent in everyday speech as the literal "mistake someone/something for something else" construction the verb started from. "Mistaken identity," a set legal and journalistic phrase, keeps the adjective locked to that one specific noun almost as a fixed collocation, appearing constantly in crime reporting and courtroom drama regardless of how rarely "mistaken" pairs with other nouns in ordinary conversation.
Across the tense system
"Mistaken" appears constantly in the passive construction "be mistaken for" ("she was mistaken for her sister"), a pattern shared with its parent verb "take," which similarly forms passive constructions like "be taken for granted," reflecting how both verbs extend naturally into passive, non-agentive uses. The active-voice form "mistook" tends to appear instead whenever the sentence's real focus is on the person doing the misidentifying rather than on the person or thing being misidentified.
Common real mistakes
A common error is using "mistaken" where the simple past "mistook" is required ("she mistaken him for someone else" instead of "she mistook him for someone else"), the same take/taken confusion that shows up with the parent verb. Learners occasionally also produce "mistaked" by over-regularizing, ignoring the inherited take/took/taken pattern entirely. A subtler slip involves the preposition: "mistake" pairs with "for" ("mistake him for a stranger"), not "as" or "with," and substituting either of those reads as noticeably off to a native speaker even though the intended meaning stays clear.
Examples
- She mistook him for his older brother at the reunion.
- He has mistaken kindness for weakness before, to his regret.
- They mistook the noise for thunder, not realizing it was fireworks.
- I was mistaken about the meeting time and showed up an hour early.
- The waiter mistook our table for a party of six.
- We had mistaken the trail marker and ended up lost for an hour.
- You're mistaken if you think this will be easy.
Memory trick
Group "mistake" with its parent verb "take" and its cousins "shake" and "forsake" — all four share the identical took/taken-style pattern. And remember "mistaken" often stands alone as a plain adjective ("you're mistaken"), separate from its use describing an action performed on a mixed-up person or object. Picture grabbing the wrong coat off a rack by accident — that's the literal image behind "mistake," long before it drifted into meaning any kind of error at all.