i-adjective
a long time has passed; long-standing; old, from long ago
Describes a long span of elapsed time, not physical length. Common in patterns such as 〜てから久しい, 久しく〜ない, and in phrases like 久しい昔の話 for something from long ago.
父が亡くなってから、もう久しい。
It has already been a long time since my father passed away.
彼とは久しく会っていない。
I haven't seen him for a long time.
That is now a story from long ago.