costly

costly — adjective

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

1.adjectiveB1
Definition

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

Example

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

Common collocations
  • costly repairs
  • costly litigation
  • costly equipment
  • costly renovation
Synonyms
  • 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

Antonyms
  • cheap

    costing very little; opposite in both price and seriousness

  • inexpensive

    neutral opposite; not costing a lot of money

Grammar Patterns

costly + noun (attributive)

be + costly (predicative)

too costly + for + noun / to-infinitive

Usage Note

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.

Common Mistakes

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.adjectiveB2
Definition

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

Example

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

Common collocations
  • costly mistake
  • costly error
  • costly failure
  • costly delay
  • costly decision
  • costly war
Synonyms
  • 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

Antonyms
  • beneficial

    producing good results; opposite of harmful

  • profitable

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

Grammar Patterns

costly + noun (attributive)

prove / turn out to be costly

costly mistake / error / failure

Usage Note

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.

Common Mistakes

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.

Word family

  • cost
    nounA2
  • cost
    verbA2
  • costless
    adjectiveC1
  • costliness
    nounC2

Synonym discussion

Sense: adjective/1

All five words describe something that costs a lot of money, but they differ in tone and context. 'Costly' is more formal and often implies a burden or sacrifice beyond simply the price — a costly legal battle suggests financial strain, not just a high bill. 'Expensive' is the neutral, everyday word for anything that costs a lot. 'Pricey' is informal and slightly gentler — a nice but pricey little café sounds friendly rather than critical. 'Overpriced' has a negative, critical tone: the speaker believes the item is not worth what is charged. 'Dear' is chiefly British and somewhat old-fashioned, often used when prices seem unfairly high ('Petrol is so dear these days'). For example, you would call a new hospital wing 'costly' (focus on the burden of funding it), a restaurant meal 'expensive' (neutral fact), a souvenir shop's T-shirt 'overpriced' (not worth the money), and a café latte 'pricey' (casual observation).

costly ↗expensive ↗priceyoverpriced ↗dear ↗

Common collocations

Nouns

  • costly mistake
  • costly error
  • costly failure
  • costly decision

Adverbs

  • extremely costly
  • prohibitively costly
  • increasingly costly
  • financially costly

Phrases

  • prove costly
  • turn out to be costly

Etymology

LatinOld FrenchEnglish

'Costly' was formed in English during the 14th century by adding the suffix '-ly' (which turns nouns into adjectives, as in 'friendly' or 'kingly') to the noun 'cost' (meaning 'price, expense'). The original meaning was simply 'expensive'. The metaphorical sense — 'involving great loss or sacrifice' — developed in the 17th century, extending the idea of high cost from money to other kinds of harm.