noun
pixel density
Technical term used in digital imaging and display contexts, equivalent to PPI (pixels per inch) or similar measures.
このスマートフォンは画素密度が高いので、画面がとても鮮明です。
This smartphone has a high pixel density, so the screen is very sharp.
解像度 refers to resolution (total pixel count), while 画素密度 specifically refers to pixel density (pixels per unit area).
Compound of 画素 (pixel) and 密度 (density).