usher
/ˈə-shər/
noun
an officer or servant who has the care of the door of a court, hall, or chamber
an officer who walks before a person of rank
one who escorts persons to their seats (as in a theater)
verb
to conduct to a place
to precede as an usher, forerunner, or harbinger
to cause to enter : introduce
verb
to serve to bring into being
to mark or observe the beginning of
a discovery that ushered in a period of change