惭愧 cánkuì ashamed

How to remember 惭愧: 惭 ashamed + 愧 ashamed = ashamed.

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The feeling of being ashamed of your own shortcoming or of not measuring up - 让您费心了,我很惭愧 (ràng nín fèixīn le, wǒ hěn cánkuì) I'm ashamed to have troubled you so much.
Unlike 羞耻 (xiūchǐ, shame/disgrace, moral), 惭愧 is softer and self-directed - regret at falling short of an expectation, often used as a polite deflection when praised.
Common set phrase: 感到惭愧 (gǎndào cánkuì, to feel ashamed). Register is neutral-to-humble.