by the hour是什么意思
英语有些词“单位词”，如hour, day, month, year, dozen, gallon, ton, yard等，当它们表示标准含有类似汉语的“按”“论”“每”等义时，其前原则上要用定冠词。如：
They let out cars by the day. 他们按天出租汽车。
The cloth is sold by the yard. 这种布是按码卖的。
They are paid by the hour. 他们所得报酬按小时计。
Do you sell eggs by the kilo or by the dozen? 鸡蛋怎么卖，论公斤，还是论打?
Is gasoline sold by the gallon in America? 在美国，汽油是以加仑出售的吗?
但是，by weight(按重量)习惯上不用冠词。如：
Bananas are usually sold by weight. 香蕉通常按重量卖。