Provably
The Century Dictionary and Cyclopedia
In a manner capable of proof.
Wiktionary, Creative Commons Attribution/Share-Alike License
adverb.
With
proof
; in a provable manner.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adverb.
in an obvious and provable manner
Word Usage
"How about one more apology for being willfully, deliberately and provably wrong?"
Synonym
Words with the same meaning
demonstrably