Here's why:
* Adverbs modify verbs, adjectives, or other adverbs, providing information about time, place, manner, or degree.
* "-ward" indicates direction or movement towards something.
Examples:
* backward: (adverb) moving in the opposite direction
* forward: (adverb) moving in the direction ahead
* homeward: (adverb) moving towards home
* downward: (adverb) moving in a downward direction
It's important to note that there are some cases where "-ward" might be attached to a word to form a noun or adjective, but these are less common.