Etymology Usage

Is the stock market predictable?

Q: I’ve googled and googled “predictive” and “predictable,” but it’s still not clear when I can use one and not the other. If stock prices can be predicted, is the market “predictable” or “predictive”? I can’t quite put my finger on the difference between these two words. Are they interchangeable?

A: The verb “predict” comes from Latin roots and literally means “pre-say.” A parallel word with Anglo-Saxon roots is “foretell.”  

If something is “predictive,” it helps to predict or foretell something else—some situation or event. And that situation or event is what’s “predictable”: it can be predicted or foretold.

So “predictive” and “predictable” events are not interchangeable. One does the predicting (it foretells). The other is what’s predicted (it’s foretold).

Another point to make here is that logically what’s “predictive” precedes what’s “predictable.” 

Here are some examples:

“A fall in housing prices is predictive of a recession,” said the analyst. “In other words, the recession was predictable after housing prices fell.”

And here’s another, more whimsical set of examples:

“This love line in your palm is predictive of a happy marriage,” said the fortune teller. “Furthermore, your happy marriage was predictable because of that love line.”

As for the stock market, it’s “predictable” if stock prices can be predicted. And it’s “predictive” if a rise or fall in the market predicts good times or bad.

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