In
morphology (a subfield of
linguistics), a compound is a (relatively) new word created by the
word formation process of (surprise!) compounding. Usually, compound is short for compound
noun, because the compound word is a noun, though the other word may be of any
lexical category.
How do compounds differ from noun phrases?
Compounds are any combination of words (generally two in
English) that have come to be represented as one word in the
mental lexicon of the speakers, unlike noun phrases, which are thought of as a combination of multiple words which can be switched around (i.e., noun phrases are
productive.) The same words can be used as a compound noun or a noun phrase (see examples below), so telling the difference between these two things is often difficult (and something a number of my
Introduction to Linguistics students always get wrong) when the compound is a combination of an adjective and a noun. When you have a noun-noun compound (like
enchilada sauce) they are easier to identify, but still must pass the
intonation test below.
This is all well and good, but how can we identify a compound?
The
testable difference between compounds and noun phrases
in English, is which part of the word or phrase is
stressed. Rather than the
head receiving stress, as happens in phrases (we say black
bird because it is a bird, not a black), the first item receives stress, regardless of whether it is the head or not (and it usually is not, because of how English
syntax works).
For example:
black
bird = could be a raven, crow, blackbird (noun phrase)
vs.
blackbird = a specific species of bird (compound)
white
house = any house that is white in color
vs.
White House = where the
president of the united states lives
make
up = a verb phrase meaning to create something (as a story), to prepare something for use (as a bed), or to make amends after a fight
vs.
makeup = cosmetic products
or
make-up = the composition of something
(Note that the spelling is generally different between a noun phrase and its compound counterpart; this in and of itself, however, does not tell us whether a word is a noun phrase or compound noun, as in makeup and make-up which are both compounds but
have different meanings. Spelling is often altered in situations like these because readers do not have the benefit of intonation to help their understanding of a sentence, but
linguists are much more interested in how the
language is spoken, not how it is written. Spoken language reveals much more about
how language works than do things like
spelling conventions.)