禁不住 (jīn bu zhù) is a verb with two related senses: 'can't help (doing something)' — an involuntary emotional reaction — and 'can't bear / can't withstand' — a physical or mental inability to endure. Unlike the adverb 不禁 (bù jīn, 'can't help but'), which only modifies a verb, 禁不住 can stand as a predicate and also expresses physical incapacity. For the 'can't bear' sense, 受不了 (shòu bu liǎo) focuses on endurance rather than capacity.