Warn is defined as to tell or caution against danger.(verb)
An example of warn is to tell someone that there is a slippery road ahead.
See warn in Webster's New World College Dictionary
Origin: ME warnien < OE wearnian < IE base *wer-, to heed > guard
See warn in American Heritage Dictionary 4
verb warned, warn·ing, warns verb, transitive
Origin: Middle English warnen
Origin: , from Old English warnian; see wer-4 in Indo-European roots.
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