Backward-Backwards | Commonly Confused Words

Backward

/ˈbækwəd/

In the reverse direction from what is usual or expected

The software is compatible with backward systems.He has a backward approach to modern problems.She was held back by backward thinking policies.

/ˈbækwədz/

In reverse or opposite direction.

'Know her, Sir! why, she was always coming backwards and forwards."You got it backwards.He suddenly threw himself backwards.

Backward can be both an adjective and an adverb, while backwards is strictly an adverb.
Backward is often used in American English, while backwards is more common in British English.
Remember that forward does not take an s, similar to the American use of backward.
Think of backward as equivalent to forward in style.
To check usage, replace with forward/forwards and see which version matches.