And now, Words and Their Stories, a VOA Learning English program about American expressions.

When you are learning a language, context is everything. Here, "context" means the words around another word or phrase that help explain what the sentence is saying. And context is even more important for a certain group of words – words that are their own opposites.

A word with opposing meanings is called a contronym or contranym, spelled with an "a."

These words also go by the more romantic term "Janus words." Janus is the Roman god of beginnings and endings. He is often shown with two faces looking in opposite directions.

So, what are these Janus words? Some are very common, like the word "off."

If you turn off a device or light, you deactivate it. But if you say a device went off, you mean it was activated. Here's an example using a car alarm.

Imagine. It's late at night. Your neighbor's car alarm starts making a loud noise. The noise wakes you up. So, you go to your neighbor's apartment to tell him.

"Hey! Hey, wake up! Your car alarm is going off. Turn it off before it wakes up the whole neighborhood!"

The word "left" is another example of a contronym. "Left" can mean either to depart from a place or to remain in a place. For example, the women left the dinner party to sit outside. The guys were left in the kitchen to clean up. Here, the women departed the party, leaving the men to remain in the kitchen.

I really like that example.

Here are some examples of contronyms from the world of farming.

If you seed a tomato or cucumber, you remove the seeds. But if you seed a field, you put seeds in a field to grow.

Dust is another word that requires some context for understanding. Dust as a noun means fine particles of something, such as dirt or ash. Dust as a verb can mean either to add or to remove those fine particles.

So, if you are cleaning a house, you can dust furniture by removing dirt. Or, if you are farming, you can dust crops by adding anti-insect dust, usually by airplane.

Context is everything. Another common word is fast.

Fast can mean something is moving quickly: she is running fast. But "fast" can also mean something is fixed and unmoving. For instance, if colors are fast they will not run when you get them wet.

Here's another example: "Hold fast to your beliefs. Don't change them simply because they are unpopular at the moment."

Another contronym is the word "screen." Screen can mean both to show and to hide. You invite many families to your house for the screening of your new film. You can't wait for them to see it. But when the film shows a violent image, you hold your hands over the children's eyes and screen their view.

Also, if you are screening candidates for a job, you are choosing not to see some of them. We also say we are screening phone calls if we are choosing to answer some but not others. Yet many of us look at a computer screen every day to see pictures, get information and of course check VOA Learning English.

And that's all for this Words and Their Stories. Really. I mean it. There's no contronym in that sentence.

I'm Anna Matteo.

See ya!