“In the Pipeline” vs “Lined Up” vs “Set in Stone”: C1 Idioms Explained

Some English expressions look almost the same but mean different things, and that’s exactly where C1 learners get caught out. In this episode I was batch cooking in my kitchen while practising idioms out loud with an AI assistant (Claude), and we focused on a group of expressions about how ready something is.

Here’s the clear version, with examples you can use straight away.

In the pipeline

If something is in the pipeline, it’s still in development. It’s being actively worked on and moving through several stages, but it isn’t ready yet.

• We’ve got a new series on football idioms in the pipeline.
• More job losses are in the pipeline.
• Another 200 cases are in the pipeline.

The image is a real pipe: something enters at one end, travels through, and comes out finished at the other. That’s why it fits projects, products and plans so well.

Lined up

If something is lined up, it’s already arranged and ready, just waiting for its turn, like people in a queue.

• I’ve got a few interviews lined up for next week.
• Mark had a job lined up when he left college.
• I’ve got a lot lined up this week. (= I’m very busy)

The literal picture helps: products lined up on a shelf, sitting ready for someone to pick them up.

Set in stone

If something is set in stone, it’s completely fixed and can’t be changed.

• Nothing’s set in stone yet, so we can still make changes.
• Once the contract’s signed, the deal is set in stone.

The readiness scale

Think of these three as a journey:

1. In the pipeline: still being prepared (least ready).
2. Lined up: arranged and waiting.
3. Set in stone: fixed and final (no flexibility left).

Or, as the AI put it in a cooking metaphor I loved: in the pipeline is still cooking, while lined up is already plated and ready to be served.

Expressions for finally understanding

Then the conversation moved on to another family of expressions: what we say when we suddenly understand something.

It clicked

When something clicks, it suddenly makes sense, like a switch flipping on.

• I didn’t get it at first, but after you explained it again, it just clicked.

It also works for people who get on well immediately: We met and just clicked.

The penny dropped

The penny dropped is very British. It means you finally understood or realised something, often after a moment of confusion. Picture an old slot machine: you drop a coin in, there’s a little pause, and then it falls and the mechanism works.

• It took me a while, but the penny finally dropped when he explained it with a diagram.

I’d recently watched the Oasis documentary about their comeback, and Liam Gallagher uses this expression. He says “the penny’s dropped”, with the h of the auxiliary has completely gone, which is really common in natural British speech. As I understood it, he meant it was time to grow up and take the band seriously.

Sink in

Sink in is a phrasal verb, not an idiom. It describes something gradually becoming fully understood, especially surprising or emotional news.

• It hadn’t really sunk in that I’d passed until a few hours later.
• The news took a while to sink in.

Literally, it’s water slowly soaking into soil. So compare: it clicked is instant, the penny dropped is sudden after a pause, and sink in is slow.

Bonus: idioms for memory

At the end of the stream, the summary also covered a set of memory idioms from earlier sessions. They’re perfect for C1 speaking:

• It’s on the tip of my tongue: I almost remember it, but not quite.
• That rings a bell: it sounds familiar.
• I drew a blank: I couldn’t remember anything at all.
• It all came flooding back: I suddenly remembered everything.
• Bite off more than you can chew: try to do more than you can manage.

A tip for learning idioms with AI

AI tools are great speaking partners, and practising out loud while you cook is a fantastic habit. But here’s my advice: always check the examples in a proper dictionary, like the Cambridge or Longman online dictionaries. They give you real examples from real texts, and they’ll catch anything the AI gets slightly wrong.

Practice

Complete each sentence with in the pipeline, lined up, set in stone, clicked, the penny dropped or sink in.

1. The dates aren’t ___ yet, so we can still move the meeting.
2. I’ve got three job interviews ___ for Monday.
3. The company has two new apps ___, but they won’t be ready until next year.
4. It took weeks for the news to really ___.
5. I stared at the maths problem for ages, and then suddenly ___.

Watch the episode

The full episode shows the conversation in real time, so you can hear how I check and question the AI’s examples. It’s a good model for your own practice sessions.

Subscribe for more C1 idioms and my CEFR prep series. And tell me in the comments: which of these expressions finally clicked for you?