Idioms are fixed lexical chunks with a specific meaning that often cannot be worked out from analysis of the literal meaning of the words used, although those words do have a literal meaning and, in some cases, once the meaning of the idiom is known, an analogy can be made - as in the first, second and third examples below.
- to bark up the wrong tree
- to beat around the bush
- to hear something on the grapevine
- to let the cat out of the bag
- to take something with a grain of salt
Other idioms are more transparent in meaning, as in eg It's pouring with rain / It's tipping it down.
See also : My teacher is an old cow : Teaching figurative language, should we or shouldn't we?
Lewis, M. implementing the Lexical Approach, CENGAGE ELT
(Don't forget that Amazon often have copies of the books you want at prices much lower than the advertised price. it's alwatys worth checking - and no, we don't earn anything rom your clicks.)