In some of the compounds that we have looked at so far, relationships are expressed that are the same as ones expressed in syntax: for example, the verb–object relationship between hair and restore in hair restorer. On the other hand, the way in which the verb–object relationship is expressed in this compound is quite different from how it is expressed in syntax, in that the two words appear in the opposite order: we say This substance restores hair, not *This substance hair-restores. There is a clear difference between compound word structure and sentence structure here. But there are also complex items that function as words, yet whose internal structure is that of a clause or phrase rather than of a compound. There is no standard term for these items, so I will introduce the term phrasal words.

An example of a phrasal word is the noun jack-in-the-box. Structurally this has the appearance of a noun phrase in which the head noun, jack, is modified by a prepositional phrase, in the box, exactly parallel to the phrases people in the street or (a) book on the shelf. However, it forms its plural by suffixing -s not to the head noun (as in books on the shelf) but to the whole expression: not ‘jacks-in-the-box’ but jack-in-the-boxes, as in They jumped up and down like jack-in-the-boxes. Though structurally a phrase, then, it behaves as a word. Contrast this with another item which is at least as idiosyncratic in meaning and which has a superficially similar structure: brother-in-law. A crucial difference is that brother-in-law forms its plural by affixing -s not to the whole expression but to the head noun: brothers-in-law. Despite its hyphens, therefore, brother-in-law is not a word at all but a phrase.

Can phrases other than noun phrases constitute phrasal words? The answer is yes. Adjectival examples are dyed-in-the-wool (as in a dyed-in-the-wool Republican) or couldn’t-care-less (as in a couldn’t-care-less attitude). Syntactically, dyed-in-the-wool looks like an adjective phrase consisting of an adjective (died ‘artificially colored’) modified by a prepositional phrase, just like suitable for the party or devoted to his children. However, such a phrase cannot entirely precede the noun it modifies (we say a man devoted to his children or suitable music for the party, not *a devoted to his children man or *suitable for the party music); therefore the behavior of dyed-in-the-wool is that of a word rather than a phrase. As for couldn’t-careless, its structure is that of a verb phrase, but again its behavior is that of an adjective (e.g. Your attitude is even more couldn’t-care-less than hers!).

This seems an appropriate point to mention a small and rather old-fashioned class of lexical items exemplified by governor general, attorney general, court martial and lord lieutenant. How do they form their plural: like attorney generals, or like attorneys general? If you prefer the former, then these items may seem at first like further phrasal words – except for the fact that they differ from normal English noun phrases in having an adjective following the noun rather than preceding it. It seems better, therefore, to treat them as examples of something that we have not so far encountered: endocentric words which, untypically, have their head on the left rather than on the right. On the other hand, if you prefer the latter sort of plural (attorneys general), they seem more akin to brother(s)- in-law: not words but lexicalized phrases. If, finally, neither kind of plural sounds quite right to you, that is not surprising, because however these items are analyzed, their structure is unusual.