a dime a dozen – this expression comes from the U.S. A dime is a coin worth 10 cents so it has little value. A dozen in English is another way of saying the number 12. So if you can buy 12 things for 10c, it means they are very cheap. The idiom a dime a dozen therefore means that something is not worth very much or can be found very easily. Example sentence: It’s hard to find blueberries here but they’re a dime a dozen in Australia.
run-of-the-mill – this saying is more typical of British than American English. It means that things are very ordinary or uninteresting. Example sentence: What did you think of the new Italian restaurant? Not much really. It was rather run-of-the mill.
as common as….
- as common as muck
- as common as dirt
- as common as mud
These three sayings taking the form of similes and all mean that something is so common that it is not very special at all. The association of common with dirt & much is also not a very positive one. Example sentence: Pigeons are as common as muck around here.
However, you must be careful if you use these idioms to make an association with people. The word ‘common’ in English can also have a very negative meaning. It can be used to express the idea that someone has no class or education. Example sentence: I don’t know why she married him. His family are as common as muck.