Non-separability and integrity
Two more diagnostics for wordhood involve the notions of non-separability and integrity. Words differ from larger units, such as phrases, in that they cannot be broken up by the insertion of segmental or phrasal material. (For the moment, we’ll ignore infixes.) This characteristic of words is called non-separability. Likewise, syntactic processes cannot apply to pieces of words. This is integrity. Adjectives and adverbs, for example, modify words, not morphemes. Words and phrases are often displaced to the beginning of a sentence or questioned, but not morphemes:
(7) a. Now, that one I like.
Which one do you like?
b.*Possible, it’s im-.
*Which school did you see bus? (i.e., Which school’s school bus did you see?)
Non-separability and integrity diagnostics tell us that compounds like doghouse, greenhouse, and school bus consist of a single word, rather than a pair of words.
Let’s begin with doghouse. We know this is a single word because we can’t put anything inside it or modify the internal components in any way. We can’t distinguish between a doghouse and a *dogshouse, where a doghouse is a house for one dog and a dogshouse for two or more.
The same restrictions hold for greenhouse. If we break up the components in any way (8a) or try to modify only a part (8b), the meaning ‘warm glassed-in structure for growing plants’ gets lost:
(8) a. a green and blue house
a greener house
b. a very green house
*a very greenhouse
It happens to be the case that the way we write doghouse and greenhouse reflects their status as single words. But orthography cannot always be relied upon as a diagnostic. Deer tick is also a compound, but it is generally written as two words. Modifiers must modify the whole compound, not just a part (so a brown deer tick is not a tick that lives on brown deer, but is instead itself brown), and its components are non-separable (*deer brown tick is impossible, though brown tick is perfectly acceptable, because we can’t reach inside a compound and separate its components).
