essence
释义：“本质、精髓”，用于在句子中呈现相对于事物庞杂外在特性的最根本部分。这个词语还能组成一个来自于法律术语的习惯用语time is of the essence，意即“时间是至关重要的”或“时不我待”。
例句：
At its essence, NASCAR is an ear-blasting, exhaust-spewing, gas-guzzling celebration of unbridled horsepower.
Cameron, the British prime minister, told parliament today that time is of the essence in Libya.