Past Tense of “buy”
The past tense of buy is bought; the past participle is bought.
Why “buy” behaves this way
"Buy" descends from Old English "bycgan," a weak verb whose past tense "bohte" underwent the same consonant-cluster simplification and vowel shortening seen in "think/thought" and "seek/sought," producing the modern "bought." All four of these verbs belong to a small historical cluster where an original "-cg-" or "-c-" sound shifted to a "-ght-" spelling and sound over the centuries, which is why they still rhyme with one another today (bought, thought, sought, fought).
This shared "-ought" rhyme across several unrelated-seeming verbs (buy, think, seek, fight) is a genuine historical fossil of a single sound change that affected an entire class of Old English weak verbs at once, rather than a coincidence — a useful pattern for spotting other members of the same family, including "bring/brought" and "catch/caught," once a learner knows to listen for it.
The common confusion
"Bought" itself is stable enough that it rarely confuses anyone; the real usage nuance is figurative "buy" (accept or believe something, as in "I don't buy that excuse") versus the literal financial sense, both sharing the identical bought/bought conjugation.
How it's actually used
"Buy" extends into a common informal figurative sense meaning to accept or believe a claim ("I'm not buying it"), a metaphor treating belief as a kind of purchase or transaction. "Buy time" (delay an outcome to gain an advantage) and "buy into" (commit to believing or supporting an idea) are two further idioms extending the financial sense of the verb into non-monetary contexts involving trust or delay. Real estate and finance treat "buy" as precise technical vocabulary within formal transactions ("buy low, sell high"), while everyday conversational "buy" covers everything from groceries to major purchases without any change in register. "Buyer's remorse," a common informal phrase describing regret after a purchase, extends the verb into a specific, widely recognized emotional and psychological pattern.
Across the tense system
"Bought" functions as a standalone adjective in the fixed phrase "bought and paid for," describing something fully, unambiguously owned or, more figuratively, someone whose loyalty has been completely secured through payment or favors, a use with a notably cynical connotation in political and business writing. "Bought" in the passive construction ("the company was bought by a larger competitor") is standard in business journalism describing acquisitions, distinct from the everyday active sense of a person purchasing a personal item, and often omits who ultimately benefited from the sale.
Common real mistakes
"Bought" is settled enough that conjugation errors are rare; the more common slip is confusing it with the unrelated "brought" (from "bring"), two words that look and sound similar but come from entirely different verbs and carry entirely different meanings. A separate, purely idiomatic mix-up is treating figurative "I'm not buying it" as overly casual for formal writing, where a plainer verb like "accept" or "believe" fits the register better. A related mix-up for learners is treating "buy" and "pay" as interchangeable, since English requires a direct object after "buy" ("buy a car") but treats "pay" differently, often requiring "for" before the item purchased ("pay for a car"), a preposition pattern that doesn't exist in every language. A final subtlety: "buy out" (purchase someone's entire share or interest in a business) is a distinct financial phrasal verb from plain "buy," specifically implying the complete acquisition of an existing stake rather than an ordinary purchase. A final stylistic note: in formal writing, figurative "I'm not buying it" should generally be replaced with "I don't accept that" or similar, since the idiom's casual tone can clash with an otherwise professional register.
Examples
- She bought a new car last weekend.
- They have bought this brand for years without any issues.
- He bought himself some time by asking a follow-up question.
- We had bought all our supplies before the store closed.
- This shop buys and sells used furniture.
- I don't buy that explanation for a second.
- She's buying a house in the countryside.
- That excuse won't buy you any sympathy here.
Memory trick
Group "buy/bought" with "think/thought," "seek/sought," and "fight/fought" as sharing the same historical "-ought" rhyme family, and remember figurative "buy" (believe, accept) as a completely separate sense from the literal financial one, though both share the identical conjugation.