  Idioms are unlike other phrases in two important ways. First, the words in an
idiom have unconventional meanings. Second, the unconventional meaning of words
in an idiom are contingent on the presence of the other words in the idiom.
Linguistic theories disagree about whether these two properties depend on one
another, as well as whether special theoretical machinery is needed to
accommodate idioms. We define two measures that correspond to these two
properties, and we show that idioms fall at the expected intersection of the
two dimensions, but that the dimensions themselves are not correlated. Our
results suggest that idioms are no more anomalous than other types of phrases,
and that introducing special machinery to handle idioms may not be warranted.
