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

As it’s applied today, the law allows trial attorneys to prey on the state’s small and mid-sized businesses — filing frivolous, costly lawsuits over even the most minor violation of California’s complex labor code. —Tom Manzo, Oc Register, 6 Apr. 2026

After installing the upgrades, federal customers would be effectively locked in, because shifting to a competitor after the free trial would be cumbersome and costly. —Renee Dudley, ProPublica, 6 Apr. 2026

That long trip is costly, particularly for gas station owners. —Chris Isidore, CNN Money, 6 Apr. 2026

Between there and the national park’s Douglas Environmental Center in Gary’s Miller neighborhood will be another costly section, with some bridge replacements in store. —Doug Ross, Chicago Tribune, 5 Apr. 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