To children, non-native English speakers, and anyone who confronts a fixed expression for the first time, they can be baffling. A fixed expression is a little like a secret code that allows access to a club that not everyone can enter. It’s a phrase that has a very specific meaning that can’t be expressed any other way and also can’t be deduced just by considering the sum of its parts. Some fixed expressions, like “ready, aim, fire” are used so often that the opportunity to turn them into a joke creates another fixed expression. Others, such as “before you know it” or “to tell you the truth” have been around for so long that they function almost as a single word.
Unlike idioms, fixed expressions typically offer neither folk wisdom nor an image. “Two heads are better than one” creates a bizarre, yet effective, visual idea of one body that operates with two heads, while the idiom’s meaning is that two people working on a problem have a better chance of solving it than just a single thinker. Fixed expressions are more often a collection of words with individual meaning that really have nothing to do with one another.
“All of a sudden” is a perfect example. “All” means a totality, a location or moment in time in which everything is included. “Of a” is really just a grammatical phrase with no internal meaning of its own. “Sudden” refers to something completely unexpected; it is only the final word in this expression that contributes meaning to the fixed expression, which is simply another way of saying “suddenly.”
Another charmingly baffling fixed expression is “neither here nor there.” This phrase is used to dismiss someone’s idea, statement, or concern as being irrelevant. In effect, if something that has been added to a conversation is “neither here nor there,” then it’s nowhere; it doesn’t exist and can therefore be ignored.
Sometimes, fixed expressions really make very little sense. Imagine two friends who are discussing which movie to see. One tells the other, “It’s up to you,” meaning that the friend should make the decision. As the word “decision” isn’t anyplace in the phrase or even suggested by it, unless a listener already knows what the phrase means, there’s no way to understand it.
Learning fixed expressions is part of learning a language. Children often question a fixed expression the first time they hear it but quickly absorb the meaning and integrate it into their conversations. English learners, however, must make a concerted effort to memorize fixed expressions because they are such an important part of communication in English.