effectiveness

Estimated CEFR level: C2 — Proficiency

Estimated from word frequency; not an official CEFR classification.

Definition

noun power to be effective; the quality of being able to bring about an effect
noun capacity to produce strong physiological or chemical effects

From effective + -ness.

The term applied to the quality of effectiveness. — Practical Mechanics for Boys, James Slough Zerbe
Effectiveness of assertion is the Alpha and Omega of style. — Man and Superman: A Comedy and a Philosophy, Bernard Shaw
Krishna bustles round packing things--bustles is hardly the word though, for his barefooted, silent effectiveness. — From Edinburgh to India & Burmah, W. G. (William Gordon) Burn Murdoch

effectivity, effectualness, effectuality

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