Learner's definition of MERCURY
1 [noncount]
a : a silver metal that is liquid at normal temperatures汞；水银
b : the mercury in a thermometer that shows the air's temperature水银柱 -
In the summer, the mercury can reach over 100 degrees Fahrenheit.夏天，水银柱可超过100华氏度。
-
By late afternoon, the mercury had dropped (to) below zero.傍晚时，气温降到了零度以下。
2
Mercury [singular] : the planet that is closest to the sun水星（距离太阳最近的行星）