Assiduous, a.
Etymology: [L. assiduus, fr. assid to sit near or close; ad + sed to sit. See Sit.]
1. Constant in application or attention; devoted; attentive; unremitting. She grows more assiduous in her attendance. Addison.
2. Performed with constant diligence or attention; unremitting; persistent; as, assiduous labor. To weary him with my assiduous cries. Milton.
Syn. -- Diligent; attentive; sedulous; unwearied; unintermitted; persevering; laborious; indefatigable. As*sid"u*ous*ly, adv. -- As*sid"u*ous*ness, n.
Shades of meaning
Fernald has no entry of its own for assiduous; he lists it under industrious.
He lists it without comment; the entries above explain its neighbors.