doubtless
adv.without any doubt. You use this to say that something is almost certainly true, even if you cannot prove it yet.
adv.used to express that something is very likely or certain to happen or be true. Often used to concede a point before introducing a contrasting idea.
“He will doubtless succeed in his new job.”
“The new policy will doubtless cause some confusion among the staff during the first few weeks of implementation.”
“While the critic acknowledged the film's technical brilliance, he noted that it would doubtless struggle to find a wide audience due to its experimental narrative structure.”
Sentence adverb — often placed after the first auxiliary verb or at the start of a clause to indicate the speaker's certainty.
“Photograph: David Levene/the Guardian Computer-generated renderings are a perpetual hostage to fortune, and MVRDV went gangbusters on Rotterdam ROCKS!, doubtless in an attempt to seduce the competition jurors.”
“Once that deal is done attention will doubtless turn to filling the midfield chasm left by Tonali and Guimarães.”
From Middle English douteles, dowteles, equivalent to doubt + -less.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.