Pronounced m4 goi1 in Cantonese — the most-used politeness word in Hong Kong. Distinct from 多谢 (do1 ze6): 唔该 is for service and small favors ('please / excuse me / thanks for the help'), while 多谢 is for real gifts or serious gratitude.
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唔 (m4) is the Cantonese negative 'not', and 该 (goi1) means 'should'. Literally 'shouldn't have to trouble you' — a humility formula that became the everyday 'thanks'. Universally understood across Canton and HK.
