A harbinger is a sign that something is coming, like an early warning or preview of what lies ahead. When you see robins hopping across your lawn in March, they're harbingers of spring. When dark clouds gather on the horizon, they're harbingers of an approaching storm.

The word often carries a sense of anticipation or foreboding. A harbinger doesn't cause what's coming; it simply announces it. If your teacher starts a sentence with “We need to talk about your grades,” those words are a harbinger of a serious conversation ahead. When a friend shows up at your door with a big smile and a mysterious box, that smile might be a harbinger of good news or a surprise gift.

Historically, a harbinger was a person who rode ahead of a royal party to arrange lodging and announce their arrival. This original meaning helps explain why we still use the word for anything that comes before and signals what's following behind. You might hear someone describe a new invention as a harbinger of technological change or call an early symptom a harbinger of illness. The word suggests that if you pay attention to the harbinger, you won't be caught off guard by what comes next.