Something that anticipates, predicts or foretells.(noun)
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Use "predictor" in a sentence
"Now let's turn to the second element, unit labor costs, which I also see as a good short-term predictor of inflation."
"It is also used as a short-term predictor of investor behavior."
"Or Facilitate It. TechCrunch on Marketwatch who are adding digg like functionality to stock codes, neat: The predictor is a small widget included on every stock listing page (example)."