How do you pronounce "costly"?

In American English: /ˈkɑːstli/ (KAHSTL-ee). In British English: /kˈɒstli/ (K-ostl). In Canadian English: /ˈkɑːstli/ (KAHSTL-ee). In Australian English: /kˈɒstli/ (K-ostl).

Is "costly" pronounced differently in American and British English?

Yes. In American English it's pronounced /ˈkɑːstli/ (KAHSTL-ee), while in British English it's /kˈɒstli/ (K-ostl).

How to Pronounce "costly"

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costly

regional

/ˈkɑːstli/

KAHSTL-ee

Syllable Breakdown

kɑːstlcost·ily

Source

90%confidence📘 CMU Pronouncing Dictionary v0.7b

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Last updated: 2026-02-14