The Only Use of

herald
in
The Alchemist, by Coelho

Yesterday, the camel's groan signaled danger, and now a row of date palms could herald a miracle.
p. 89.1

herald = be a sign of

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)
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.