Diligent, a.
Etymology: [F. diligent, L. diligens, -entis, p. pr. of diligere, dilectum, to esteem highly, prefer; di- = dis- + legere to choose. See Legend.]
1. Prosecuted with careful attention and effort; careful; painstaking; not careless or negligent. The judges shall make diligent inquisition. Deut. xix. 18.
2. Interestedly and perseveringly attentive; steady and earnest in application to a subject or pursuit; assiduous; industrious. Seest thou a man diligent in his business he shall stand before kings. Prov. xxii. 29. Diligent cultivation of elegant literature. Prescott.
Syn. -- Active; assiduous; sedulous; laborious; persevering; attentive; industrious.
Shades of meaning
Fernald has no entry of its own for diligent; he lists it under active, industrious.
Where he writes about it:
Active refers to both quickness and constancy of action; in the former sense it is allied with agile, alert, brisk, etc.; in the latter, with busy, diligent, industrious. — from active
The active love employment, the busy are actually employed, the diligent and the industrious are habitually busy. — from active
Diligent indicates also a disposition, which is ordinarily habitual, and suggests more of heartiness and volition than industrious. — from industrious
We say one is a diligent, rather than an industrious, reader of the Bible. — from industrious