An idiotic modern word that has crept out of technical use in game theory to compete in pseudo-intellectual discourse with the real English word satisfying the same part of speech (effectiveness), which should be used instead in almost every case. Not to be confused with efficacy, which actually has a different meaning.

In manufacturing, which instances of a complicated product get a particular version of a part. Effectivity was coined at Boeing, in their old factory-control software, to identify a specific airplanes on the assembly line.