This is the 4419th most frequent Polish word.
istotnych
"Essential" or "important."
Here, 'istotnych' is used as an adjective modifying 'rzeczy' (matters), indicating their importance.
To są istotnych rzeczy, które musimy omówić.
These are important matters that we need to discuss.
In this sentence, 'istotnych' serves as an adjective describing 'wpływ' (impact), denoting the considerable effect.
Nasze działania mają istotnych wpływ na środowisko.
Our actions have a significant impact on the environment.
In this example, 'istotnych' qualifies 'tematów' (topics), highlighting their significance.