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

Switching hardware also means changing the software systems built around Nvidia’s CUDA platform, creating a costly engineering challenge for model developers. — Neetika Walter, Interesting Engineering, 11 Aug. 2026

What’s more, changing vaccine ingredients would require new studies, which would be costly and take years. — Brenda Goodman, CNN Money, 11 Aug. 2026

Dozens of Russian drone incursions into Romanian airspace have occasionally caused damage and forced Romania to respond with costly fighter jet interceptions to shoot down some of the wayward drones. — Jeremy Hsu, ArsTechnica, 11 Aug. 2026

Fairview’s board thought hard before committing to such a costly venture, but had a dream, said Edie Kalin, president of the Odd Fellows Home of CT. — Don Stacom, Hartford Courant, 10 Aug. 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