costly

/ˈkɒstli/ (bre, ipa) · /ˈkɔːstli/ (ame, ipa) · /ˈkȯs(t)-lē/ (ame, mw)

costly — adjective

  • costlypositive
  • costliercomparative
  • costliestsuperlative

1. costing a very large amount of money, often more than what is reasonable or nece

1.形容詞B1
釋義

costing a very large amount of money, often more than what is reasonable or necessary for most people.

例句

The repairs to Yumi's old house proved far more costly than the builder had estimated.

collocation: costly repairs

Dewi decided against buying the designer bag because it was too costly for her monthly budget.

pattern: too costly for [sb's] budget

同義詞
  • expensive

    neutral, everyday word for anything that costs a lot; less formal than costly

  • pricey

    informal and conversational; gentler tone than costly

  • overpriced

    critical tone, implies the item is not worth what is charged

反義詞
  • cheap

    costing very little; opposite in both price and seriousness

  • inexpensive

    neutral opposite; not costing a lot of money

文法句型

costly + noun (attributive)

be + costly (predicative)

too costly + for + noun / to-infinitive

用法筆記

Commonly used for big expenses (housing, medical treatment, legal fees) rather than everyday purchases. For casual conversation about regular items, 'expensive' or 'pricey' sounds more natural.

常見錯誤

❌This sandwich is costly.
✅This sandwich is expensive / pricey.
💡'Costly' sounds overly formal for everyday items; use it for major expenses.
❌The costly cheap dress was on sale.
✅The cheap dress was on sale. / The costly dress was beautiful.
💡'Costly' and 'cheap' are opposites; they cannot describe the same item.

2. causing serious problems, major losses, or significant harm that is difficult to

2.形容詞B2
釋義

causing serious problems, major losses, or significant harm that is difficult to recover from.

例句

Publishing the story without checking the facts proved a costly error for Saira.

collocation: costly error

The company's costly failure to update its security software allowed hackers to access customer data.

collocation: costly failure

同義詞
  • damaging

    broader range; can describe physical, reputational, or financial harm

  • devastating

    stronger and more emotional; suggests destruction rather than just loss

  • ruinous

    formal and dramatic; implies total financial or structural collapse

反義詞
  • beneficial

    producing good results; opposite of harmful

  • profitable

    producing financial gain; the direct opposite of a costly failure in business

文法句型

costly + noun (attributive)

prove / turn out to be costly

costly mistake / error / failure

用法筆記

Subject is typically an action, decision, event, or failure — not a person. Very common in business, legal, and military contexts to describe outcomes with serious consequences.

常見錯誤

❌I made a costly decision to buy a sandwich.
✅I made a costly decision to invest without checking the contract.
💡For the damaging sense, 'costly' must involve a serious loss, not a routine purchase.