IPA: /ɪˈfɛktɪvnəs/
KK: /ɪˈfɛktɪvnəs/
The quality or ability of producing a desired result or effect.
The effectiveness of the new marketing strategy was evident in the increased sales.
Effectiveness → It is formed from "effect" (from Latin "effectus", meaning accomplishment or result) and "-ness" (meaning the state or quality of). The word "effectiveness" refers to the quality of producing a desired result or effect.
Think of the word 'effect' which means to accomplish something, and '-ness' which indicates a state. This helps you remember that effectiveness is about the quality of achieving a result.