Standard Lemma guide

inefficacious

adj · 3 senses · updated from the 2026-07-25 local source snapshot

Definitions and examples are grouped by meaning. Pronunciation, history, word forms, translations, descendants, synonyms, antonyms, derived terms, and related words appear whenever the source provides them.

Sound

Pronunciation

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  • rhymes with -eɪʃəs

1

adj

Meaning 1

Incapable of having the intended consequence.

Definition source: English Wiktionary via Wiktextract

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

2

adj

Meaning 2

Not effective.

Definition source: English Wiktionary via Wiktextract

No example sentence was provided for this meaning.

Meaning relationships

Synonyms: none provided

Antonyms: none provided

3

adjective

Meaning 3

lacking the power to produce a desired effect

Definition source: Princeton WordNet 3.0

Examples

  • laws that are inefficacious in stopping crime

Meaning relationships

Synonyms: none provided

Antonyms: efficacious

History

Etymology

Etymology tree Proto-Indo-European *né Proto-Indo-European *n̥- Proto-Italic *n̥- Latin in-bor. Middle English in- English in- English efficacious English inefficacious From in- + efficacious.

Across languages

Translations

2 source translations are retained for this English entry.

  • Bulgarian: неефективен (neefektiven) — Incapable of having the intended consequence
  • Bulgarian: неефикасен (neefikasen) — Incapable of having the intended consequence