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[kawst-lee, kost-] /ˈkɔst li, ˈkɒst-/
adjective, costlier, costliest.
costing much; expensive; high in price:
a costly emerald bracelet; costly medical care.
resulting in great expense:
The upkeep of such a large house is costly.
resulting in great detriment:
It was a costly mistake because no one ever trusted him again.
of great value; very valuable; sumptuous.
lavish; extravagant.
Origin of costly
First recorded in 1350-1400, costly is from the Middle English word costli. See cost, -ly
Related forms
costliness, noun
overcostliness, noun
overcostly, adjective
uncostly, adjective
1. dear, high-priced. See expensive. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for costly
Contemporary Examples
Historical Examples
  • He gave me a costly ring, which I wear on my finger till now.

    Hania Henryk Sienkiewicz
  • Whatever the cause the costly error had shaken his faith in Jennings.

    The Man from the Bitter Roots Caroline Lockhart
  • Free ventilation and cleanliness appear to be the best preservatives against this costly evil.

    The Sailor's Word-Book William Henry Smyth
  • He asked Forester which was the most costly of all the woods.

    Forests of Maine Jacob S. Abbott
  • There were four hundred vessels of silver of great weight, and many other rich and costly articles.

    Peter the Great Jacob Abbott
British Dictionary definitions for costly


adjective -lier, -liest
of great price or value; expensive
entailing great loss or sacrifice: a costly victory
splendid; lavish
Derived Forms
costliness, noun
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for costly

late 14c., from cost + -ly (1). Earlier formation with the same sense were costful (mid-13c.), costious (mid-14c.).

Online Etymology Dictionary, © 2010 Douglas Harper
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