expression
A literary, somewhat old-fashioned adverbial phrase meaning to work steadily and diligently without giving up. Often used in formal or written contexts.
彼は孜々として研究に励んだ。
He devoted himself assiduously to his research.
孜々として働く姿は周囲の模範となった。
His diligent work set an example for those around him.
A casual adverb meaning busily or diligently. 孜々として carries a heavier, more serious tone.
The kanji 孜 means 'industrious' or 'diligent'. The phrase is a classical Chinese-derived expression (孜孜として) used in literary Japanese. The exact historical derivation is uncertain, but it follows the pattern of reduplicated kanji adverbs.