This is the 4305th most frequent Polish word.
ekranu
"Ekranu" means "of the screen" in English.
Here, 'ekranu' is used in the genitive case to denote the object being touched—the screen.
Dotknął ekranu, aby rozpocząć prezentację.
He touched the screen to start the presentation.
In this sentence, 'ekranu' is used in the genitive case indicating possession or association, referring to the screen to which the brightness belongs.
Jasność ekranu była zbyt wysoka.
The screen's brightness was too high.
Here, 'ekranu' is in the genitive case, used to describe the origin of the reflection—the screen.