An idiom is a fixed phrase: night and day is a huge difference, buy into means believe, and a hazy idea is a vague one.
Idioms are fixed phrases
Not "The results were night and days." — say "The results were night and day.". An idiom keeps its exact words.
Try it: Ethan: Did the cafe staff like the new opening hours? Mei: Not at first, but they ___ them in the end. Choose the words for the blank. (bought into / bought / bought in) Answer: bought into — The idiom is buy into an idea, meaning accept it, while "bought" alone means paid for it.
Word
Pronunciation
Example
night and day
/naɪt ənd deɪ/
The two drafts are night and day; the second one is far clearer.
buy into
/baɪ ˈɪntu/
The team quickly bought into the new schedule once they saw the results.
a hazy idea
/ə ˈheɪzi aɪˈdiə/
I only had a hazy idea of what the report was asking for.
Idioms for talk, not reports
These idioms suit talk, not reports: a game changer is a big change, a deal-breaker ends a deal, barely moved the needle means little effect.
Not "This is deal-breaker." — say "This is a deal-breaker.". A deal-breaker is a countable noun, so it needs a.
Try it: Ethan: Has the new bus line helped you get to class? Mei: Totally. It's been ___. I'm there in ten minutes now. Choose the words for the blank. (a game changer / a deal-breaker / a ton) Answer: a game changer — A change that transforms things is a game changer, while "a deal-breaker" ends a deal.
Word
Pronunciation
Example
a game changer
/ə ˈɡeɪm ˌtʃeɪndʒər/
For the small clinic, online booking was a game changer.
a deal-breaker
/ə ˈdil ˌbreɪkər/
A long commute would be a deal-breaker for most of the applicants.
barely moved the needle
/ˈbɛrli muvd ðə ˈnidəl/
The discount barely moved the needle on our monthly sales.
Idioms for size and direction
A huge step up is an improvement, a ton is a lot, going downhill fast means worsening, and things could go south warns of trouble.
Not "Revenue is going downhill fast. (in a report to shareholders)" — say "Revenue is deteriorating rapidly.". A formal report uses the neutral wording.
Try it: Mei: The festival guide says the tickets cost a substantial amount. Ethan: So in plain English, they cost ___. Choose the words for the blank. (a ton / a huge step up / going downhill fast) Answer: a ton — A ton is the casual way to say a substantial amount.
Try it: Ethan: Did the new study schedule help your grades? Mei: Not really. Honestly, it ___. Choose the words for the blank. (barely moved the needle / was a huge step up / was night and day) Answer: barely moved the needle — Almost no change is barely moved the needle, while "night and day" means a huge difference.
Word
Pronunciation
Example
a huge step up
/ə hjudʒ stɛp ʌp/
The new lab is a huge step up from the old one.
a ton
/ə tʌn/
They spent a ton on advertising last quarter.
going downhill fast
/ˈgoʊɪŋ ˈdaʊnhɪl fæst/
Sales have been going downhill fast since the recall.
things could go south
/θɪŋz kʊd goʊ saʊθ/
If we miss the deadline, things could go south quickly.
What are the common mistakes?
Incorrect
Correct
Why
The results were night and days.
The results were night and day.
An idiom keeps its exact words.
This is deal-breaker.
This is a deal-breaker.
A deal-breaker is a countable noun, so it needs a.
Revenue is going downhill fast. (in a report to shareholders)