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efficacious

adjective

/ˌɛf.ɪˈkeɪ.ʃəs/

Meaning

Successful in producing a desired or intended result; effective.

Effective for a specific purpose

The vaccine proved highly efficacious in preventing infections.

This medicine is highly efficacious in treating headaches.

effective, potent, successful, Effective, Productive, Efficient

Entry 1

effective, potent, successful

Entry 2

Effective, Productive, Efficient

ineffective, inefficient, futile, Ineffective, Useless, Inefficient

Entry 1

ineffective, inefficient, futile

Entry 2

Ineffective, Useless, Inefficient

having already been used

not conforming with accepted or orthodox standards or beliefs

Coming after something in time; following in time or order.

not fully developed; lacking emotional or intellectual development; childish

happening or done without delay

likely to happen; expected; plausible