I need to know whether it is correct to call any series of words an “expression.” Examples:

"The study of natural phenomena has continued for centuries, with significant discoveries being made in recent years."

"The speed of light is constant in a vacuum, but it is slower when light passes through transparent substances."

"There are various ways to generate electricity, including the use of hydroelectric stations and solar cells."

Is it correct to call the highlighted words in each of the above sentences an expression?

Some people say that the word “expression” refers to a common or idiomatic phrase. But I have been freely using the word “expression” with reference to any group of words which follow one after another, such as in the above examples which do not contain any idiomatic phrases but simply state facts.

[Added on 9/11/2018:]

There was a discussion on one forum where some people said that the word “expression” does not refer to any sequence of words but to a particular phrase which is commonly used:


It seems that although some people may think that the word “expression” refers to a commonly used phrase, such as an idiomatic statement, it can be used in linguistic contexts with reference to any series of words which have a grammatical meaning. If this is correct, can the following highlighted series of words be called “expressions”?

‘As the lightning,” he says, shall he come; not concealed in any corner, but shining everywhere.’”

“We must always be doing this so that if our Lord should ever suddenly come to take us, he may find us carrying this out and then assign a reward far greater than that promised earlier to the one properly carrying out his instructions.”

  • 1
    According to which authority do you wish to determine its "correctness"? I would use it only for a sequence of words which formed a constituent in the grammar of the sentence. But others may have a different view.
    – Colin Fine
    Commented Jul 7, 2018 at 16:01
  • I need to determine the correctness of the usage of the word according to the standard rules presented in textbooks and dictionaries.
    – Alexander
    Commented Jul 8, 2018 at 15:49
  • 1
    And what makes you think that textbooks and dictionaries have "standard rules" about the meanings of words?
    – Colin Fine
    Commented Jul 8, 2018 at 23:14
  • Textbooks and dictionaries come from respected sources and are used in schools. So the rules presented in them are accepted as standard.
    – Alexander
    Commented Jul 9, 2018 at 15:48

1 Answer 1


The word expression doesn't have to mean common or idiomatic phrase, for example the Merriam-Webster dictionary defines it simply as:

a significant word or phrase

(other definitions)

What's inarguable is that it has to have some sort of logical meaning. So while the first two of your examples are "expressions", the last one really isn't, because "generate electricity, including the use of" alone doesn't mean anything, it's not a grammatical phrase (- a sequence of words that have meaning, especially when forming part of a sentence.) and therefore not an expression - at least that's how I see it.

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