Question. (The title hopefully states the abstract question in full.)

Additional question: do you know more examples, possibly even clearer examples than "electron cloud" below.


  • An example is

electron cloud

Both A=electron and B=cloud are usual nouns, and so is "electron cloud", yet an "electron cloud" is neither an electron, nor a cloud (in the water-vapour-sense).

  • A non-example is "red herring": while it is true that a "red herring" in general is neither "red" nor a "herring", "red is not a noun.
  • 2
    Most AB noun compounds using metaphors (like electron cloud, red herring, and lion heart) are neither A nor B, literally, because metaphoric uses are not literal. And most language is metaphoric.
    – jlawler
    Commented Aug 3, 2017 at 23:27

2 Answers 2


This is a good question, but your example is not a good one. An “electron cloud” is indeed not a cloud in the original sense of the word “cloud” (in the atmosphere), but it is a “cloud” in the figurative sense of a nebulous cluster. A better example would be something like “lion heart”, which is not a lion and not a heart, but a person whose heart (here in the sense of “bravery”) is like that of a lion. This is an example of what in linguistics is called a “bahuvrihi” or “exocentric compound”.

  • Many thanks for this. "Exocentric compound" is certainly applicable: it is general enough to cover "electron cloud" or "lion heart", yet not as all-encompassing as "idiom". However, I do not understand how "bahuvrihi" applies: all (words usually called) bahuvrihis in English known to me are of the form "adjective noun", and if one goes to the Sanskrit, it seems to get farther from "lion heart" still, in that (0) they seem to have the form "adjective-like-word noun", but the bahuvrihi itself in Sanskrit is an adjective (while neigher "electron cloud" nor "lion heart" is an adjective).
    – guest
    Commented Aug 8, 2017 at 7:13
  • A bahuvrihi can function as an adjective or as a noun (“she is a red-head”); the first component is often an adjective, but it can also be a noun (Skt prajā-kāma- “whose wish is offspring; Gk rhodo-daktylos “whose fingers are roses”).
    – fdb
    Commented Aug 8, 2017 at 9:38

It is Idiom or, more specifically, idiomatic expression.

It is widely accepted that idioms break the principle of compositionality which, in turn, can be expressed as "the meaning/value of a composition can be deducted from individual meanings/values of its parts". Idioms quite often don't follow this rule.

…[U]se of segmentally complex expressions whose semantic structure is not deducible jointly from their syntactic structure and the semantic structure of their components. — Weinreich (1972:89)

  • Thanks. Yet shouldn't there be some much more specific technical term than "idiom" (which to me can describe just about any phenomenon of a meaning not being deducible from the constituent parts of an expression, when the parts are given out of order, say). Does someone know something more specific? In particular, some literature reference which both treats "red herring" and (something similar to) "electron cloud"?
    – guest
    Commented Aug 3, 2017 at 8:37

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