Contrary to popular beliefs, idioms show a high degree of formal flexibility, ranging from word-like idioms to those which are like almost regular phrases. However, we argue that their meanings are not transparent, i.e. they are non-compositional, regardless of their syntactic flexibility. In this paper, firstly, we will introduce a framework to represent their syntactic flexibility, which is developed in Chae ( 2014 ), and will observe some consequences of the framework on the lexicon and the

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... et of rules. Secondly, there seem to be some phenomena which can only be handled under the assumption that the component parts of idioms have their own separate meanings. However, we will show that all the phenomena, focusing on the behavior of idiom-internal adjectives, can be accounted for effectively without assuming separate meanings of parts, which confirms the non-transparency of idioms.