Definition of prerogatively in US English:

prerogatively

adverb

  • By way of prerogative or privilege; by an exercise of prerogative.

Origin

Late Middle English; earliest use found in Secreta Secretorum. Apparently from prerogative (although this is first attested slightly later) + -ly.

Pronunciation

prerogatively

/prɪˈrɒɡətɪvli/