The compound word 幸亏 (xìngkuī) is formed by combining two distinct characters, each contributing to its overall meaning of "fortunately" or "luckily". The first character, 幸 (xìng), carries the core sense of "good fortune" or "luck". The second character, 亏 (kuī), originally means a "deficiency" or "loss", but in this context, it functions to emphasize reliance or dependence on that good fortune, implying "thanks to" or "owing to". Together, they create an adverb that grammatically introduces a favorable outcome that has occurred despite potential difficulty, essentially meaning "it is only due to good fortune that"... The formation thus encapsulates a sense of grateful relief, where a fortunate circumstance has compensated for or averted an unfavorable situation.