The Eyebrow reference article from the English Wikipedia on 24-Apr-2004
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Eyebrow

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The eyebrow is a bony ridge above the eye, found in humans and other primates. In humans, it bears a tuft of facial hair, one purpose of which appears to be to prevent debris (e.g. dandruff) falling into the eyes.

Many females pluck their eyebrows with tweezers, a time consuming process.