Responsive vs. Adaptive vs. Mobile
Responsive and adaptive web design are closely related, and often transposed as one in the same.
Responsive generally means to react quickly and positively to any change, while Adaptive means to be easily modified for a new purpose or situation, such as change.
With Responsive design websites continually and fluidly change based on different factors, such as viewport width, while Adaptive websites are built to a group of preset factors.
Mobile, on the other hand, generally means to build a separate website commonly on a new domain solely for mobile users.
Responsive web design, favoring design are currently the most popular technique that dynamically adapts to different browser and device viewports, changing layout and content along the way.