backwards

Compared meaning: toward the back, in the opposite direction (adverb).

比较义项：向后地，朝相反方向（副词）。

• backward

  More typical in American English as the adverb of direction; unlike backwards, it can also function as an adjective before a noun (a backward glance) — that use is not compared here.

  作方向副词时在美式英语中更常用；与 backwards 不同，它还能作形容词修饰名词（如 a backward glance，此处不作比较）。

  He took a step backward when the dog barked loudly.

  狗大声叫的时候，他向后退了一步。

• backwards 本词

  More typical in British and other Commonwealth English as the adverb of direction; it only works as an adverb, never as an adjective before a noun.

  作方向副词时在英式及其他英联邦英语中更常用；它只能作副词，不能像 backward 一样作形容词修饰名词。

  He accidentally put his shirt on backwards this morning.

  他今天早上不小心把衬衫穿反了。

Backward and backwards both mean toward the back or opposite direction, and are almost interchangeable. The difference is regional: backward is common in American English, and backwards is common in British English. Backward can work as an adjective, as in 'a backward glance', not compared.

这两个词在“向后、朝相反方向”这个副词义项上几乎可以互换，主要区别在于地域用法习惯：backward 在美式英语中更常见，backwards 在英式及其他英联邦英语中更常见；此外 backward 还能作形容词修饰名词（如 a backward glance，此处不作比较），backwards 没有这种形容词用法。