in an important way or to an important degree
"more importantly, Weber held that the manifold meaning attached to the event by the social scientist could alter his definition of the concrete event itself"
in an important way
"for centuries jellies have figured importantly among English desserts, particularly upon festive occasion"
Used to mark a statement as having importance.
"Importantly, the new policy will significantly reduce carbon emissions by next year."
In plain English: Importantly means that something is very significant and deserves your attention because it matters a lot.
"Importantly, she made sure to check all her tickets before leaving for the concert."
Usage: Use importantly only when describing how an action was performed with care or significance, such as in the phrase "he listened importantly." To emphasize that something is significant rather than describing manner, use the adjective important instead.
From important + -ly.