costly

adjective

cost·​ly ˈkȯs(t)-lē 

costlier; costliest

1

a

: commanding a high price especially because of intrinsic worth

costly gems

b

: rich, splendid

2

: made or done at heavy expense or sacrifice

a costly mistake

costliness noun

Synonyms of costly

• expensive
• valuable

Examples of costly in a Sentence

We use less costly materials in our products.

It was too costly to fix her car after the accident, so she decided to buy a new car instead.

They won the game, but their best player was injured, so it was a costly victory.

The decision to wait could be a costly mistake.

Recent Examples on the Web

In theory, testing virtual designs will cut down development cycles, predict equipment degradation, and avoid costly trial-and-error during physical builds. — Aman Tripathi, Interesting Engineering, 5 Nov. 2026

Newsom and other opponents of capital punishment have long argued that the process is costly, cruel and discriminatory, with death sentences disproportionately handed down to defendants of color. — Sonja Sharp, Los Angeles Times, 5 Nov. 2026

While some prediction market betting has been argued to have societal value — for instance, a company hedging against a costly change in government policy — Mitts notes betting on entertainment industry news isn’t really one of them. — James Hibberd, HollywoodReporter, 5 Nov. 2026

If a Democratic Congress makes the data center buildout slower or costlier, some of that demand story will fade. — Harvey Stober, CNBC, 5 Nov. 2026

Word History

First Known Use

14th century, in the meaning defined at sense 1a

Kids Definition

costly

adjective

cost·​ly ˈkȯs(t)-lē 

costlier; costliest

1

: of great cost or value

costly furs

2

: gained at great expense or sacrifice

a costly victory

costliness noun