1. The functional constituents of phrases
Kuiper and Allan Chapter 7.1.2

2. Heads and modifiers Phrases have heads.
Heads determine the grammatical properties of the phrase.
Grammatical properties are distributional properties,
i.e. where units come relative to one another.

3. Exercise Look at the distribution of in a train.
a. Granville met his beloved in a train.
b. You always get an odd range of smells in a train.
c. The emergency cord in a train should not be touched without good reason.

4. Now look at the distribution of a train.
a. *Granville met his beloved a train.
b. *You always get an odd range of smells a train.
c. *The emergency cord a train should not be touched without good reason.
Which grammatical category determines the distribution of in a train?

5. More about heads Heads are normally obligatory.
Heads are semantically central.
Non-heads are modifiers.