A lot of IELTS students don't really know the difference between using idioms and using idiomatic language . Idiomatic can mean using and idioms , such as; We get on like a house on fire . BUT We get on really well , means exactly the same and is perfectly idiomatic You |DON'T need to use a lot of idioms in your IELTS speaking and writing tests, but you DO need to use idiomatic language. Sounds confusing, but it isn't really. In the Cambridge dictionary there are 2 definitions for 'idiomatic' 1 Containing an idiom. It was raining cats and dogs and i got soaked ./ drenched = very wet Nobody say this these days! 2 Containing expressions which are NATURAL and CORRECT It was raining heavily and I got soaked . This is perfectly natural and correct and therefore IDIOMATIC English. Don't waste your time trying to pack your speaking and writing with loads of idioms. Native speakers , especially the younger generation, don't use them often.