An early Tang dynasty encyclopedia compiled by [[虞世南|虞世南|yu2 shi4 nan2]]; one of the four great encyclopedias of the Tang dynasty. Its name derives from the northern hall of the Imperial Library where Yu worked during the Sui dynasty. It is highly valued for preserving fragments of ancient texts that are now lost.

Eulogistic phrase used to express condolences for the death of a mother or an elderly woman; literally the daylily in the north hall has withered.