How to Pronounce “efficacy”

American (US)

/ˈɛf.ɪ.kə.si/

British (UK)

/ˈɛf.ɪ.kə.si/

Australian (AU)

/ˈef.ɪ.kə.si/

noun — The ability to produce a desired effect under ideal testing conditions.

Where the stress falls. “efficacy” has 4 syllables, and the transcription /ˈɛf.ɪ.kə.si/ puts the primary stress mark (ˈ) before the first one — so the first syllable is the longest and loudest. The others are said quickly and lightly.

An unstressed vowel reduces to schwa. /ˈɛf.ɪ.kə.si/ contains a schwa /ə/ — the short, neutral “uh” that English unstressed syllables collapse into. Saying /ə/ there, instead of the vowel the spelling suggests, is most of what makes the word sound native.

What does "efficacy" mean?

efficacy (noun): The ability to produce a desired effect under ideal testing conditions.

How do you pronounce "efficacy" in American vs British English?

Both accents use the same sequence of phonemes for "efficacy", /ˈɛf.ɪ.kə.si/, so the difference you hear is in how the vowels are coloured rather than in which sounds are used. Play both on this page to compare.

What is the IPA transcription of "efficacy"?

/ˈɛf.ɪ.kə.si/ in American English, /ˈɛf.ɪ.kə.si/ in British English, /ˈef.ɪ.kə.si/ in Australian English.

Which syllable is stressed in "efficacy"?

“efficacy” has 4 syllables, and the transcription /ˈɛf.ɪ.kə.si/ puts the primary stress mark (ˈ) before the first one — so the first syllable is the longest and loudest. The others are said quickly and lightly.