noun, noun, used as a prefix
Used as a noun or prefix to indicate a great length in space or time. Often appears in literary or formal contexts, and in compounds like 長きにわたる (over a long period/distance).
長きにわたるご支援に感謝いたします。
We are grateful for your long-standing support.
彼は長き旅路の末、故郷にたどり着いた。
After a long journey, he finally arrived at his hometown.
The common adjective meaning 'long'. 長き is a more formal, noun-like form often used in writing or set phrases.
Derived from the classical Japanese attributive form of the adjective 長し (ながし), which corresponds to modern 長い (ながい). The form 長き is now used as a noun or prefix in modern Japanese.