永恒
yǒnghéng · HSK 7
eternal
♾️ 永恒 = 永 forever + 恒 constant; two lasting words stacked into one endless one
永 (yǒng) means forever and 恒 (héng) means constant or enduring. Both halves already carry the sense of lasting, so doubling them up makes a word for the never-ending: eternal, perpetual.