Retina display is a trademark used by Apple for displays claimed to have pixel density so high that the eye would not be able to notice pixelation. The term is used for several models of the iPod touch, iPhone, iPad, and MacBook Pro.
Retina Display is a brand name used by Apple for liquid crystal displays that have a pixel density high enough that the human eye is unable to discern individual pixels at a typical viewing distance. The term is used for several Apple products, including the iPhone, iPod Touch, iPad, MacBook Pro, iPad Mini, and iPad Air. Because the typical viewing distance is different, depending on each device's use, the pixels per inch claimed to be of Retina quality can differ, depending on the size of the display, with higher PPI for smaller displays and lower PPI for larger displays: 326 PPI for the smallest devices (iPhone, iPod Touch, and iPad Mini with Retina display), 264 PPI for mid-sized devices (iPad third generation and onwards, including iPad Air), and 220 PPI for larger devices (MacBook Pro). While not currently common, many other manufacturers' displays have similar PPI density. When an Apple product has a Retina Display, each user interface widget is doubled in width and height to compensate for the smaller pixels. Apple calls this mode HiDPI mode. Apple has applied to register the term "Retina" as a trademark in regard to computers and mobile devices with the United States Patent and Trademark Office, Canadian Intellectual Property Office, and in Jamaica.On November 27, 2012 the US Patent and Trademark office approved Apple's application and "Retina" is now a registered trademark for computer equipment.
Source: Wikipedia (Retina Display)
