inscribe a debt of gratitude on one 's mind
It is hard to forget.
Idioms and allusions
Source: the 96th chapter of Xu Zhonglin's Fengshen romance in Ming Dynasty: "my concubines are deeply loved by your majesty. They are unforgettable."
Discrimination of words
Synonym: Unforgettable usage: as predicate and attribute; metaphor: painstaking thinking
inscribe a debt of gratitude on one 's mind
be in harmony in appearanc but at variance in heart - mào hé xíng lí
write cursive characters in a vigorous and nimble style - jīng shé rù cǎo