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Classic usage
Pronunciation: /ˈɛf.ɪ.kə.si/
Reading level: hard
Estimated CEFR level: C1 — Advanced
Estimated from word frequency; not an official CEFR classification.
From Old French efficace, from Late Latin efficācia (“efficacy”), from efficāx (“efficacious”); see efficacious.
efficaciousness
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tap / space
Classic usage
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