This is the 4745th most frequent Polish word.
nuklearnej
"Of nuclear" or "nuclear" (adjective form).
In this sentence, 'nuklearnej' describes 'energii', indicating that it's nuclear energy.
Technologia nuklearnej energii ma wiele zalet.
The technology of nuclear power has many advantages.
Here, 'nuklearnej' modifies 'broni', referring to weapons of a nuclear type.
Problem nuklearnej broni jest tematem wielu debat.
The issue of nuclear weapons is the subject of many debates.
'Nuklearnej' describes 'fizyki', pointing to physics related to nuclear topics.