Everyday expressions where one word is fixed and cannot be swapped
He deleted the file by accident - she deleted hers on purpose
How to use this sheet
At this level you already know every individual word in these expressions. What you cannot predict is which words English has chosen and welded together. Each entry in the table is a fixed combination used constantly in everyday speech: for deciding, for helping, for staying in contact, for saying whether something was deliberate or not. The meaning of the whole is usually easy to see; the danger is producing a version of it that is almost right. Treat each row as a single item of vocabulary: learn it whole, and notice which word in it could never be guessed from the meaning alone.
| Expression | Meaning | Typical situation |
|---|---|---|
| make up your mind | finally decide | choosing between two options in a shop or on a menu |
| change your mind | decide something different from before | cancelling or switching a plan you had already announced |
| have second thoughts | start doubting a decision you have made | the night before signing a contract or accepting a job |
| keep an eye on | watch something or someone carefully | asking a stranger to watch your bag at the station |
| give someone a hand | help someone | carrying furniture, boxes or heavy shopping |
| take your time | do it slowly, without hurrying | reassuring someone who is apologising for being slow |
| keep in touch | continue to communicate regularly | saying goodbye to a friend who is moving away |
| get in touch | contact someone | starting an email to a company or an old colleague |
| it's up to you | you are the one who decides | letting a friend choose the restaurant or the film |
| on purpose | deliberately, intentionally | accusing someone, or defending yourself against blame |
| by accident | without intending to | explaining a mistake: something deleted, broken or sent |
| learn something by heart | memorise it word for word | preparing a poem, a dialogue or lines for a presentation |
In use
Sorry, I've changed my mind - can we meet on Thursday instead? Take your time - the film doesn't start until eight. I'll get in touch with the landlord about the heating.
Watch out
She spilt coffee on my laptop, but I'm sure she didn't do it by purpose.
The incorrect sentence blends the two contrasting entries in rows ten and eleven. Each of those expressions is welded to its own preposition, and the prepositions are not interchangeable: the deliberate one keeps the small word that opens row ten, the unintentional one keeps the small word that opens row eleven. Learners mix them because both phrases answer the same question - was it intended or not? - so the pair feels like one system with a single preposition. It is not: swap the small word and you produce something every native speaker notices at once, even though the meaning survives. The same discipline runs through the whole table: in row five, for example, the noun cannot be replaced by the ordinary word for assistance.