adverb taking the 'to' particle, taru-adjective
diligently; assiduously; unceasingly
Describes working hard and persistently, often with a literary or formal tone. Commonly used with verbs like 働く, 努力する, or 研究する.
彼は営々と研究に励んでいる。
He is diligently devoting himself to his research.
営々として働く農民の姿が印象的だった。
The sight of the farmers working unceasingly was impressive.
Reduplication of 営 (えい), meaning 'to carry out' or 'to manage', emphasizing continuous, diligent effort. The exact historical derivation is uncertain, but the form is established in literary Japanese.