Why do 2 devices of the same size, the same resolution, require different densities?

Question

Please take a look at IO Material Indicators :

Check out the Google Pixel and HTC One M9.

These 2 devices have the same physical size, the same number of pixels, but are said to have different pixel densities.

This contradicts my understanding of pixel density.

Which of the following is true?

• My understanding of pixel density is wrong. All information on the page is correct;
• The information on the page is incorrect;
• On HTC One M9, although the screen size is 5.0, a small portion of it is not used for display (i.e. the actual display size is smaller than the Google Pixel).
• Something I Can't Imagine

Answer 1

, , , , :

: 4. -,

(1) . dp-.

Google Pixel, , px/in - 441, HTC One M9. , . dp/in, . (2.6 3.0)

(2) (dp-)

, Google HTC dp -. dp . , , dp, View .
, 1x = 160dpi, dp .