in such a manner as could not be otherwise
"it is necessarily so"
"we must needs by objective"
by necessity
"the situation slid inescapably toward disaster"
In a manner that is impossible to avoid or prevent.
"The heavy rain made it inevitably clear that we would have to cancel the picnic."
In plain English: Inevitably means something is going to happen for sure and you can't stop it from happening.
"If you do not study for the test, you will inevitably fail."
Usage: Use inevitably rather than invariable when describing outcomes, as the latter refers to something unchanging over time. Avoid confusing this adverb with "inevitably" spelled incorrectly; ensure the final letter is an 'y' to maintain proper spelling and pronunciation.
The word inevitably comes from combining the adjective inevitable with the suffix -ly to form an adverb. It entered English as a straightforward grammatical construction that means something will certainly happen without any possibility of avoidance.