Origin: Germanic Old English suffix
Effectiveness has 3 different meanings across 1 category:
power to be effective; the quality of being able to bring about an effect
"The new marketing campaign's effectiveness was immediately apparent as sales doubled within the first week."
capacity to produce strong physiological or chemical effects
"the toxin's potency"
"the strength of the drinks"
The property of being effective, of achieving results.
"The new marketing campaign showed a dramatic improvement in effectiveness by actually increasing sales numbers within the first week."
In plain English: Effectiveness is how well something actually works to get the result you want.
"The effectiveness of the new cleaning product was proven by how quickly it removed stubborn stains."
Usage: Use "effectiveness" to describe how well something achieves its intended purpose or produces the desired result in real-world situations. It refers to the actual capability of an action, method, or product to work successfully rather than just its theoretical potential.
The word effectiveness is formed by adding the suffix "-ness" to the adjective effective. It entered English as a straightforward combination of these two parts to describe the quality or state of being effective.