This is the 197th most frequent Slovak word.
nielen
"Not only."
Here, 'nielen' is used to introduce the start of a listing or pairing, emphasizing 'not only...'.
Nielen Marek, ale aj Jana prišli na oslavu.
Not only Marek, but also Jana came to the celebration.
In this case, 'nielen' emphasizes an additional aspect or activity beyond the first mentioned.
On chce nielen pracovať, ale aj študovať.
He wants not only to work, but also to study.
Here, 'nielen' connects two areas of interest, underlining a broad scope.