Deleterious vs Efficacy - What's the difference?

As an adjective deleterious

is harmful often in a subtle or unexpected way (as for example deleterious'' effects, ''deleterious to health).

(uncountable) ability to produce a desired amount of a desired effect.

(en adjective)

harmful often in a subtle or unexpected way (as for example deleterious'' effects, ''deleterious to health).

* 1850 , :

Or might it suffice him, that every wholesome growth should be converted into something deleterious and malignant at his touch?

* (harmful) destructive, harmful, hurtful, injurious, noxious, pernicious; see also

* deleteriously

(-)

(uncountable) Ability to produce a desired amount of a desired effect.

* efficacity

* *