快递单号的英文：
tracking number

tracking是什么意思：
n. 追踪，跟踪
v. track的现在分词

photographic track
照相径迹

tracking camera
跟踪摄影机

One track-minded
单轨思维,大脑不灵活,缺乏灵活的思维能力

CD player skipping tracks
cd播放器跳轨

The camera eventally tracked away.
摄影机最终将镜头推远。

number是什么意思：
n. 数；号码；算数
v. 给…编号；计算，数

The number was fifty.
该数字为五十。

There is safety in numbers
人多势众

It was an irrational number.
这是一个无理数。

Which number on the card is a prime number?
在卡片上哪一个数字是最初的数字？

The number raised to the logarithm of a designated number in order to produce that designated number.
被升到指定数字的对数上的数量,是为了得到那被指定的数目。