Lewis & Short

aemŭlātĭo, ōnis, f. [aemulor], an assiduous striving to equal or excel another in any thing, emulation (it denotes rather the mental effort, while imitatio regards more the mode of action; but rivalitas is a jealous rivalry, and therefore used only in a bad sense, while aemulatio is employed both in a good and bad sense) Cic. thus explains this word: aemulatio dupliciter illa quidem dicitur, ut et in laude et in vitio nomen hoc sit; nam et imitatio virtutis aemulatio dicituret est aemulatio aegritudo, si eo, quod concupierit, alius potiatur, ipse careat, Cic. Tusc. 4, 8, 17. So,

  1. I. In a good sense, emulation: laudis, Nep. Att. 5; Vell. 1, 17: gloriae, Just. praef.; Tac. A. 2, 44, id Agr. 21; Suet. Calig. 19; id. Tib. 11: secundum aemulationem, in zeal, Vulg. Phil. 3, 6.
    Transf., of the imitation of nature in painting: pictura fallax est et in aemulatione naturae multum degenerat transcribentium sors varia, Plin. 25, 2, 4, § 8.
  2. II. In a bad sense, jealousy, envy, malevolence, δυσζηλία: aemulatio vitiosa, quae rivalitati similis est, Cic. Tusc. 4, 26, 56: infensa, Tac. A. 13, 19: municipalis, id. H. 3, 57: adversariorum, Suet. Ner. 23; cf. id. 33: aemulatio nasci tur ex conjunctione, alitur aequalitate, exardescit invidiā, cujus finis est odium, Plin. Pan. 84 al.: ad aemulationem eum provocaverunt, to jealousy (said of God), Vulg. Psa. 77, 58. contentiones, aemulationes, rivalries, ib. 2 Cor, 12, 20.