Alternate vs. Alternative: Which Road is Best?

Carmen writes:

Dear Snarky,
My ELA teacher told us that all the road signs that say 'alternate route' are using poor grammar, and that they should say 'alternative route' instead. Was she right?

Thanks for your question, Carmen! I hope you listened to your teacher; she is right. But in this case, being right is being lonely. It's yet another great example of where an incorrect word has weaseled its way into common usage. Your teacher pointed out the incorrect use of 'alternate route' on road signs everywhere. Another example: Our legal system uses the term 'alternate juror' when 'alternative juror' is the better choice.

Even so, it's always worthwhile to learn the rule about alternate vs. alternative, if only so you can ace it on a test and dazzle your friends with your knowledge of grammar trivia. (Tip: Be prepared to be mocked for your nerdish obsession.)

Where does the Department of Transportation go wrong? It mixes up the adjectives alternate and alternative.

Quick rules: 

• Use alternate to indicate the taking of turns. We meet on alternate Fridays.
• Also use alternate to indicate a substitute with only one choice. If you don't like that sweater in green, we offer it in an alternate color, blue. I hate alternate side parking.
• Use alternative to indicate that there is more than one other option. We need to find an alternative plan. If you don't like peas or broccoli, find an alternative vegetable to eat.

Correction: Alternative route advised.