There are some words we use so often that we don't even realize they may not mean what we think they do. Like the word "literally," for example. If you watch the comedy Parks and Recreation, you know how much Rob Lowe's character loves using it. But is he always right? Literally means "the exact meaning of the word(s)" without exaggeration or inaccuracy. So if Rob Lowe says, "I literally flew down the road while running," that means he suddenly sprouted wings.
Or how about the word "less?" We often confuse it with "fewer." Here's the trick: "less" refers to a quantity that can't be counted; "fewer" refers to numbers. Saying there were less vegetables available at the Farmer's Market is not correct. You can count vegetables. Instead, you would say there were fewer vegetables available.
Kind of interesting, huh? To read about some more words that we commonly misuse, check out this fun article. (Note: Princess Bride fans will especially love it.) Thanks to OCM's Paula Seeger for suggesting this topic.