necessary

adjective
1

Required, essential, whether logically inescapable or needed in order to achieve a desired result or avoid some penalty.

"Although I wished to think that all was false, it was yet necessary that I, who thus thought, must in some sense exist."

2

Unavoidable, inevitable.

"If it is absolutely necessary to use public computers, you should plan ahead and forward your e-mail to a temporary, disposable account."

3

Determined, involuntary: acting from compulsion rather than free will.

noun
1

A place to do the "necessary" business of urination and defecation: an outhouse or lavatory.

2

Necessity.

Source: https://en.wiktionary.org/wiki/necessary

Definitions come from the Free Dictionary API (dictionaryapi.dev), with Wiktionary as a fallback when it is slow, and are cached for up to 24 hours.