quintessence
/kwɪnˈtesəns/noun
1- the most perfect or typical example of a quality or class典范, 范例：
he was the quintessence of political professionalism.
他是典型的职业政治家。
1.1
- the aspect of something regarded as the intrinsic and central constituent of its character精髓; 本质; 关键：
we were all brought up to believe that advertising is the quintessence of marketing.
我们大家从小接收教育, 相信广告是市场营销的关键。
1.2
- count noun a refined essence or extract of a substance（从物质中提取的）精华。
1.3
- (in classical and medieval philosophy) a fifth substance in addition to the four elements, thought to compose the heavenly bodies and to be latent in all things（古典和中世纪哲学中除空气、水、火、土四要素以外的）第五要素, 以太。
词源
late Middle English (as a term in philosophy)： via French from medieval Latin quinta essentia 'fifth essence'.