All 3 Uses

herald
in
Oedipus King of Thebes (translated by: Murray)
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Aye, and two Heralds have sent ere now.
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heralds = people who announce important news
Four men were with him, one a herald; one Chariot there was, where Laius rode alone.
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herald = a person whose job is to announce important news
As one in daze I walked, till, at the crossing of three ways, A herald, like thy tale, and o'er his head A man behind strong horses charioted Met me.†
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Definitions:

(1) (herald as in: heralds the coming of...)
a sign that something will happen -- especially something important and good

or:

to announce or welcome -- especially with enthusiasm
(2) (herald as in: announced by herald & trumpet)
a person who announces important news -- especially a king's representative
(3) (meaning too rare to warrant focus)
More rarely, herald can also refer to an official whose specialty is heraldry (the study of coats of arms -- symbols once used to signify the right to bear arms).

Historically a herald was a person who made announcements at jousting matches, or (much more rarely) any prestigious assistant in a dignified setting such as a courthouse or royal palace.