This. Enormous pet-peeve to not differentiate. why It's certainly not a hill I'd die on, but broadly speaking, there are major differences. The proliferation of technology and associated changes in the flow of information are enormous, yet "Millennial" continues to be a lazy catch-all for "people not currently materially impactful on society who are younger than me" in many media and business settings. Many Millennials grew up without widespread internet, mobile phones, or intense airport security. Someone who's 35 generally has a different worldview and grew up in a different world than someone who's 15. Hell, even someone who's 28 grew up in a different era than someone who's 18. A kid who just graduated college probably has a hard time remembering a time when there wasn't a supercomputer connecting its user to everyone else in the world from the palm of her hand -- it's pretty cool.