koo-tan孤單

lonely

lonely; lonesome; solitary; desolate; weak; powerless; only; just; alone

adverb

English Wiktionary, “孤單” (CC BY-SA 4.0) — https://en.wiktionary.org/wiki/%E5%AD%A4%E5%96%AE · confidence: High (Wiktionary, PH/Quanzhou/Jinjiang)