adverb
endlessly; eternally; interminably
Used for something that seems to continue without limit, often with a sense of vastness or monotony. Common in literary and descriptive contexts.
果てしなく続く砂漠を歩き続けた。
We kept walking across the endlessly stretching desert.
彼の話は果てしなく退屈だった。
His story was interminably boring.
Adjectival form meaning 'endless' or 'boundless'; 果てしなく is its adverbial form.
More formal and abstract 'eternally', often used for timeless concepts, while 果てしなく emphasizes a perceived lack of end in space or time.
Adverbial form of 果てしない, from 果て (end, limit) + しない (negative of する), literally 'without end'.