What part of speech is “futile”

the adjective form of the word 'futile' describes something (usually a action, task, result, or endeavor) as being pointless, useless, or ineffective.

1. His attempts to fix the broken engine were futile in the end.

2. After years of searching, the detective's case yielded nothing but a futile result.

3. It seemed that any efforts to find peace between the two warring nations were utterly futile.