Quick answer: Expensive means having a high monetary price: That car is expensive. Costly can mean expensive, but it also means involving great loss or sacrifice of something other than money — time, reputation, or lives: The mistake proved costly. For a fuller definition, see the Cambridge Dictionary entry for ‘expensive’.
Comparison Table
| Word | Primary meaning | Non-money use? | Example |
|---|---|---|---|
| expensive | high monetary price | no | This restaurant is very expensive. |
| costly | high price OR great loss/sacrifice | yes | A costly error / a costly victory. |
Understanding Expensive
Expensive is the everyday word for something that costs a lot of money. It describes the price tag of goods, services, or experiences. It refers strictly to financial cost and cannot be used metaphorically to describe non-monetary losses.
The hotel was too expensive for our budget.
Designer clothes can be extremely expensive.
Medical treatment in the US is very expensive.
Is the new smartphone really that expensive?
Expensive vs Pricey
Pricey is an informal synonym for expensive: “That coffee shop is a bit pricey.” Both refer only to monetary cost, unlike costly which extends to other forms of loss.
Understanding Costly
Costly can describe high monetary expense, but its distinctive use is to describe something that involves serious negative consequences — loss of lives, time, reputation, opportunity, or health. It often appears in formal or written contexts and carries a more serious, sometimes tragic tone.
The campaign was a costly failure.
The delay proved costly for the project.
It was a costly mistake that damaged their reputation.
The battle was won, but at a costly price in human lives.
Common Mistakes
✗ The error was very expensive in terms of time. (awkward for non-money loss)
✓ The error was very costly in terms of time.
✗ That coffee is so costly! (sounds stiff in informal speech)
✓ That coffee is so expensive! (or pricey)
✗ A costly restaurant. (correct but unusual — expensive is natural here)
✓ An expensive restaurant. (standard everyday use for price)
Also compare: Price vs Cost, Economic vs Economical, Damage vs Harm. Browse all confusing word pairs →
Quick Check: Expensive or Costly?
Four questions — choose the correct word.
1. “The new laptop is really ___.” (high price, casual)
2. “The team’s defeat proved ___ to their championship hopes.”
3. “This was a ___ mistake — it damaged years of goodwill.”
4. “Private schools in the UK are very ___.”
Frequently Asked Questions
What is the difference between expensive and costly?
Expensive means having a high monetary price. Costly can mean expensive, but also describes anything that involves great loss or sacrifice — of time, reputation, lives, or opportunity.
Can costly mean expensive?
Yes. “A costly renovation” means an expensive one. In this use, costly and expensive overlap. However, costly sounds more formal and is less common in everyday conversation about prices.
Can expensive be used metaphorically?
Rarely. In everyday English, expensive refers to money. For non-monetary losses, costly is the right choice: “a costly mistake” (in reputation or time), not “an expensive mistake” in that sense.
Is “costly mistake” a set phrase?
Yes, “costly mistake” is a very common collocation in English. It describes an error that leads to serious consequences. “Expensive mistake” is also used, usually when the consequence is specifically financial.
Which word is more formal?
Costly tends to sound more formal or literary. In everyday speech, people say “it’s expensive” far more often than “it’s costly.” Costly is more frequent in journalism and formal writing.
What is the adverb form of expensive?
The adverb is expensively: “The flat was expensively furnished.” Costly does not have a widely used adverb form; you would rephrase: “at great cost.”
Can I say “costly war”?
Yes, and it is a natural colocation. “A costly war” implies it involved great loss of life, resources, and political capital — more than just financial cost. “An expensive war” focuses narrowly on the monetary expense.
Are costly and pricey the same?
No. Pricey is informal and refers only to monetary cost: “That restaurant is pricey.” Costly is formal and can describe non-monetary losses. They are not interchangeable.
What is the opposite of expensive?
The opposite of expensive is cheap (informal) or affordable / inexpensive (neutral). The opposite of costly (in the non-monetary sense) might be “cheap” or “consequence-free.”
Which word should I use in IELTS essays?
Use expensive for high monetary prices and costly when describing serious consequences or losses. Using both correctly in an essay demonstrates a strong command of vocabulary and register.