Pixel density
Pixel density expresses the number of pixels within a physical length, usually in pixels per inch, or PPI. It relates resolution to the size of a screen or a reproduced image
What it means, how it is used and where it comes up, with its related concepts.
What it is and how it works
It is not the same as a printer's DPI, which describes printed dots. Nor does it determine perceived quality on its own: size, viewing distance and content also matter. Interfaces additionally use logical units to adapt their presentation to screens with different densities.
Also known as
PPI, Pixels per inch