The term ‘idiom’ can refer to two types of fixed expressions. First, in a narrow sense, idioms are ‘expressions whose idiomaticity is semantic; typical expressions are kick the bucket, spill the beans etc. Second, idiomaticity is a formal property of expressions and is more or less equated with the fixedness of form; for example, by and large’ (Stathi, 2006: 27). It is more common, as Moon (1997: 46) says, for idioms to refer to ‘multi-word items which are not the sum of their parts: they have holistic meanings which cannot be retrieved from the individual meanings of the component words.’ Idioms are thought to be ‘relatively frozen and to have severe grammatical restriction’ (Moon, 1997: 47), and so it might be generally taken that they do not permit any lexical or syntactic modification, but they have greater possibilities of modification than might be expected. There are many idioms with different structures in the English language; I have chosen the idioms with the syntactic structure V + the + N. In this paper I will try to show the degrees of modification, the possible reasons for their modifications and the significance of the definite article by using the British National Corpus (BNC) and Webcorp, a web concordancer.