Also means
efficacy
Usage Note
Efectividad stresses the actual results achieved, whereas eficacia stresses the theoretical capacity to produce an effect — learners often use them interchangeably, but in formal or scientific writing the distinction matters. The adjective efectivo can also mean 'cash' (dinero en efectivo) in a completely unrelated sense.
Examples
"La efectividad del tratamiento fue comprobada."
Natural Translation
The effectiveness of the treatment was confirmed.

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