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:
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