English Compounds

I. There is no clear upper limit in number of roots allowed in English compounds (for example,  three-time loser, man about town,  mother of pearl, four-dimensional space time continuum).           

II. Some compounds are written as one word: blackbird. Some are written with hyphens: mother-in-law. Some are written as separate words: smoke screen.  Typically not spelling, but stress and word-internal sound rules distinguish compounds from non-compounds: Compare white house with White House.

III. Two-root compounds come with a number of different structures:

A.  Nouns Noun-Noun Adjective-Noun Preposition-Noun Verb-Noun
apron string high school overdose swearword
hubcap smallpox underdog whetstone
bedroom poorhouse uptone scrubwoman
schoolteacher bluebird afterthought rattlesnake
B. Adjectives Noun-Adjective Adjective-Adjective Preposition-Adjective
headstrong white-hot overwide
skin-deep widespread ingrown
nationwide bittersweet underripe
earthbound hardworking above-mentioned
C. Verbs Noun-Verb Adjective-Verb Preposition-Verb Verb-Verb
spoonfeed dry-clean outlive sleepwalk
aircondition whitewash overdo
window-shop broadcast uproot

    In each of these cases, the syntactic class of the compound is the same as the syntactic class of the final element of the compound. The compound itself can serve as the form for derivation or inflection. Thus, sunshine + -y gives the adjective sunshiny; overdo + -er gives the noun overdoer.
    One thing is clear, these compounds (like other derived forms) are internally complex and have a hierarchical structure. Consider hard-working: it is clear that hard and work cannot form a compound first to which the suffix -ing is applied. Why is that clear? Because there is no verb hard-work. Note
                    *He hard-works. *They hard-worked. *I will hard-work.
Instead, first the adjective working must be derived from the verb work, only then can hard be compounded with it. So that the internal structure of this word must be
Structure of hardworking