When you first arrive in the USA, you’ll notice a lot of differences pretty quickly. You might even hear your host family and other Americans using phrases no one ever taught you—some of which sound like total nonsense!   To help you out, we compiled a list of 10 phrases used regularly by Americans and handpicked as most helpful by former au pairs. Of course, if you hear a phrase we don’t cover, don’t be afraid to ask what it means! Soon, you’ll be using these, and many more, like a pro.    1. Step it up  When someone tells you to “step it up”, they’re asking you to do something faster or better. For example:  I know you’re tired, but there’s 10 minutes left in the game, so you need to step it up.    2. Knock it off  This is a common, casual way to say “stop it!” You might hear this used if two siblings are fighting or if the dog won’t stop barking. It’s not usually an angry comment, and more directed towards actions that are annoying or silly.    3. You’re killing me  This one is not literal—so don’t worry, you’re not actually causing anyone harm! This is simply an exaggerated way of saying that something someone said was very funny. It’s a play on the phrase “I’m dying of laughter”, which means a similar thing.    4. Shake it off   If you’re a Taylor Swift fan, you might already know this one. If someone tells you to shake it off, they’re telling you to not take offense or move on. For example, if you had a bad day, a host parent might tell you to “shake it off and get some sleep.”     5. Riding shotgun  You’ll hear this phrase often, and it’s one that au pairs are often confused by. “Riding shotgun” simply means you’re riding in the passenger seat, or next to the driver. This is considered a big privilege in the USA, so sometimes you’ll hear people “call shotgun” or reserve the passenger seat.     6. Piece of cake   When used as a phrase, this actually has nothing to do with cake. It is used to say that something was very easy to do. For example:  How did the test go?  Oh, it was a piece of cake!    7. On my way  This is another very common phrase, and something that you’ll often receive in a text. When you say “I’m on my way!” it means that you have left for the destination. An example of this would be if a parent leaves work and says “I’m on my way home!” Sometimes, Americans will use the acronym OMW.    8. Be right back  This phrase is also often texted or used with the acronym BRB. It is something you would say if you’re leaving a conversation or location briefly, maybe to use the restroom or grab a napkin. This is the same as saying “back in a second”, which under-exaggerates how brief your time away will actually be.    9. Let me know  Americans use this phrase on many occasions, as it’s a nicer way of asking someone to tell you something. For example, rather than saying “Tell me when you’re done using the TV”, a host parent may say “Let me know when you’re done using the TV” in order to sound less demanding. You could respond: “Yes, I’ll let you know!”    10. Break a leg  Here’s another misleading one. This phrase is mostly used in the context of theater or performance to wish someone good luck before their show. However, sometimes it’s used elsewhere. Before a big exam someone might tell you to “break a leg”, meaning they’re wishing you success!