Foreshadowing
Foreshadowing means that the author gives a small hint or warning about something that happens later on. Foreshadowing could be a good or bad thing. For an example: The dark eyes watched quietly from the forest. Or the sun rose and the birds were singing. The first example might warn someone about a dark creature on the prowl. The second example might hint at a good day to come.
Examples of Foreshadowing in Lord of the Flies here.
Examples of Foreshadowing in Lord of the Flies here.