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

But now, the costly contests that will decide the next two years of Congress run through Republican-friendly Iowa, Texas, Ohio and Alaska — and control of the chamber is no longer a given for either party. — Stephen Fowler, NPR, 8 Sep. 2026

Shaving down the error Instead of building costly new equipment, the team solved the issue by flattening the material’s surface using a Cooling Cross-section Polisher. — Mrigakshi Dixit, Interesting Engineering, 7 Sep. 2026

Andy Burnham and his chancellor are constrained by costly rising debt – interest on debt costs more than the defence, Home Office and justice departments combined – rigid fiscal rules, and Labour’s manifesto pledge not to raise the three main taxes. — The Week Uk, TheWeek, 7 Sep. 2026

In fact, Iamaleava’s interception at the end of the first half on Cal’s 13-yard line — something Chesney put on the receiver but Iamaleava took blame for after the contest — could have been the costliest mistake of the game. — Connor Dullinger, Los Angeles Times, 7 Sep. 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