by weight（英语问题）您好!“按重量计算” 是：by weight .但“按千克计算” 是：by the kilo .类似的还有：by the yard 等等.请问,这一类的有什么规律吗?请列举.

by就是每的意思，就是汉语的多少元/千克

介词 prep. 在…旁；靠近
near to;beside
· Our teacher was sitting by the window.
我们的老师正坐在窗户旁边。
· Stand by me!
站到我的身旁来！
· We spent our holiday by the sea.
我们在海边度假。
介词 prep. 经过
past
· He walked by me without speaking.
他走过我的身旁，没有说话。
· My brother goes by the building every day.
我弟弟每天从这楼旁走过。
介词 prep. 用；靠；通过
using (showing who or what did something)
· I know it by heart.
我把它记在心头。
· They can read by touch.
他们可以通过手摸来阅读。
· By getting up early, I can have an hour for reading English in the morning.
靠起得早，我每天早晨有一小时时间阅读英语。
介词 prep. 不迟于
not later than
· I shall be back by 5 o'clock.
最迟五点我一定回来。
· How many English parties had you had by the end of last term?
到上学期末，你们举行了几次英语晚会？
介词 prep. 通过；沿着
through; along; over
· We came through the fields, not by the road.
我们是穿过田野而不是沿那条路来的。
· to send a letter by post
通过邮局寄信
介词 prep. （表示作者）被；由
word that shows the author, painter, etc.
· Thirty divided by two is fifteen.
三十除以二得十五。
· The child was saved by a PLA man.
这孩子是由一位解放军战士救活的。
· This bridge was built by the soldiers.
这座桥是士兵们造的。
介词 prep. （指交通等）乘；用
word that shows what kind of transport, etc.
· The man came by bus.
那人是坐公共汽车来的。
· They went to Shanghai by air.
他们坐飞机去上海。
介词 prep. 在…情况下；在…时间
during
· Do you prefer travelling by day or by night?
你喜欢在白天还是在夜晚旅行？
介词 prep. （表示部分）在…部位
word that shows which part
· She led the child by the hand.
她拉着孩子的手往前走。
副词 adv. 在旁边
near
· He gave me a story book when nobody was by.
当附近无人的时候他把小说给了我。
副词 adv. 从旁边经过
past
· He hurried by without a word.
他匆匆地走过去没有说一句话。
· Time has gone by.
时间已过去了。
· She walked by.
她走过去了。

一般by 后边加的名次是具体的话,比如是按千克或是按天,就是by the kilogram ,by the day ; 不是具体的话比如时间,重量,数量,就是by time ,by weight ,by number !你可以理解的