(bound form) cannot; impossible. Historically a contraction of the characters 不 bù and 可 kě.

(literary) to endure; to withstand; same as 耐 nài

(archaic) thereupon; then; consequently.

(literary) but; however; unfortunately (expressing an unexpected turn or obstacle, often as 无奈 wú​nài or 怎奈 zěn​nài)