This is the 1582nd most frequent Polish word.
główny
Main.
Główny is used here to mean "main" or "principal", describing the primary or most important subject in context.
Główny bohater tej książki jest bardzo odważny.
The main character of this book is very brave.
Here, główna serves as an adjective, denoting that the street holds primary importance or prominence in the locality.
Nasza główna ulica będzie zamknięta na remont.
Our main street will be closed for renovation.
In this case, głównym is used to describe the most central or important purpose, aligning with its meaning of "main" or "key". This also illustrates its declension in the instrumental case.