So, a complex sentence. Grammar books make it sound scarier than it is, but really it is one main clause with at least one dependent clause tacked on, and that is about it. We stayed inside because it was raining is a good one to start with, since the first bit (we stayed inside) would be perfectly happy as a sentence by itself, while the second bit just dangles there until you give it something to hang from.
Only here for the examples? No judgement, jump straight to the 37 examples and come back later if you fancy it.
The short version
- The formula, if you want one, is independent clause + dependent clause, and honestly that is the whole trick.
- Dependent clause up front? Pop a comma after it. Dependent clause at the back? You can usually get away without one.
- Watch for the little starter words (because, although, when, if, who, which, that), since that is where most dependent clauses begin.
- Do not let the name put you off. Complex only describes how the thing is built, and plenty of complex sentences are five or six words long.
What is a complex sentence?
Right, the slightly nerdy bit. To pin down the complex sentence definition you need two bits of school grammar that most of us binned years ago. The independent clause is the self-sufficient one. It has a subject, a verb and a finished thought, so you could write it on a sticky note by itself and nobody would be confused. The dependent clause is the clingy one. Annoyingly, it has a subject and a verb as well (this is the bit people forget), but say it by itself and whoever is listening just waits for the rest, like when someone says if you get a minute and then wanders off. Purdue University's Online Writing Lab points out that the order is up to you: either one can lead.
Our favourite way to check is a bit low-tech. Put your thumb over the part beginning with because or when or who, and read whatever is still showing. With The office was quiet after everyone went home, your thumb hides after everyone went home, and The office was quiet still works fine, so there you go, it is complex.
Complex sentence structure: the formula
Independent clause + linking word + dependent clause
Grammar books have two names for the joining word, which is mildly annoying. If it is because, when, although or one of their cousins, it is a subordinating conjunction. If it is who, which or that, it is a relative pronoun. Stick because in front of it was raining and, just like that, the clause that was fine a second ago can no longer stand up by itself.
One thing trips people up here. The sneaky ones are until, before, after and since, because they can open a clause but they are just as happy opening a plain old phrase with no verb in it at all, which is why Cambridge Dictionary files until under both preposition and conjunction. The test is whether a subject and a verb turn up after the word, so have a look at these two side by side:
- I will wait until you get back from the shop. There is a clause in there (you get back), so the sentence is complex.
- I will wait until 5:30. Here 5:30 is just a time on the clock with no verb attached, which makes it a phrase, so the sentence is still a simple one.
Words that start a dependent clause
Every one of these little words is also a hint to your reader about how the two ideas connect, whether that is when something happened, why it happened, what it happened in spite of, or what has to be true first. We have sorted the common ones by meaning below, going off the lists in the University of Southern California Writing Center's guide.
| What it signals | Words to look for | An everyday example |
|---|---|---|
| Time | when, while, before, after, as soon as, since, until, once | Text me once you are off the train. |
| Cause or reason | because, since, as, now that | I skipped the gym because my knee was playing up again. |
| Contrast | although, though, even though, while, whereas | Although it was nearly midnight, the kebab shop was still heaving. |
| Condition | if, unless, provided that, as long as | If the printer jams again, just switch it off and on. |
| Place | where, wherever | Park wherever there is a gap, honestly. |
| Purpose | so that, in order that | Speak up so that the lot at the back can hear you. |
| Manner | as if, as though | He strolled in at ten as if nothing had happened. |
| Relative pronouns | who, whom, whose, which, that | The bloke who fixed our boiler left his torch behind. |
You may notice since and while turn up twice, and that is on purpose, because each one has two jobs. You will also spot however in some grammar lists online, and we think that is a slip, since it does a different job altogether. Purdue's guide files it with the words that link two full sentences, so it needs a semicolon before it and a comma after it, like this: The bus was twenty minutes late; however, we still made the start of the film.
Complex sentence rules for commas
Dependent clause first: use a comma
Lead with the dependent clause and Purdue's guide wants a comma straight after it, which makes sense when you think about it, since the comma is basically a little signpost telling the reader that the main point is about to start.
- When the bell finally rang, the whole class bolted for the door.
Dependent clause last: usually no comma
Turn it round so the clause comes last and the comma normally vanishes, no harm done.
- The whole class bolted for the door when the bell finally rang.
There is one exception worth knowing about. Clauses that set up a sharp contrast, the although kind, are the odd ones out, and the USC Writing Center keeps the comma for them even when they come last.
- The library was oddly quiet, although every window was wide open onto the high street.
Which and that clauses
This one causes endless arguments, but Purdue's guide to that and which keeps it fairly simple. Go for that, and leave the commas out, when the clause is the thing telling your reader which noun you mean. Go for which, with a comma either side, when the clause is just a bit of bonus information that the sentence could live without.
- The report that you sent on Monday had two typos in it. (It tells us which report.)
- The quarterly report, which runs to a whopping 40 pages, is due on Friday. (Extra detail about a report we already know.)
The three kinds of dependent clause
Not every dependent clause kicks off with because or when, as it happens. The Troy University Writing Center sorts them by the job they do, which is standing in for a noun, an adjective or an adverb. Some guides take that one step further and call these the three types of complex sentences, which is a little loose, but you will see it everywhere.
- Adverb clauses fill in the background on an action. Think when, why, where, how, or what has to happen first: We will kick off when Dan finally turns up with the ball.
- Relative (adjective) clauses latch on to a noun and tell you more about it. They usually start with who, whose, which or that: The trainers that I ordered a fortnight ago finally turned up today, in the wrong size.
- Noun clauses do the job a noun would normally do, so the whole clause can be the subject or the object. Look out for what, that and whether: I know what you mean, and honestly I agree.
37 complex sentence examples
The dependent clause is the bold bit in each one. We tried to keep them close to the sort of thing people actually say on an ordinary Tuesday.
Time
1. When the 7:40 to Leeds finally stopped, half the carriage stood up at once and started grabbing coats.
2. Maya checks her messages twice before she even takes her coat off at work.
3. After the rain finally gave up, we wandered down to the market and bought the last two punnets of strawberries.
4. The kettle clicked off while I was still digging through the dishwasher for a mug without a chip in it.
5. As soon as the exam results landed, the whole group chat went quiet.
6. Gran has lived in the same flat in Salford since she retired from the post office.
Cause and reason
7. Our flight sat on the tarmac for two hours because the crew were stuck on the M25, apparently.
8. Now that it stays light until half eight, the bike racks outside the station are rammed again.
9. She splashed out on a taxi since the last bus had already gone.
10. Because the file was nearly 40 MB, the email just sat in my outbox all afternoon.
11. As the corner shop had run out of bread, I came home with a bag of rice and some eggs instead.
Contrast
12. Although the maths paper was brutal, most of the class were out of the hall early.
13. The flat-pack wardrobe looked simple enough, although it took us three weekends to finish.
14. Even though he had been up since five, Sam stayed behind to help stack the chairs.
15. While I will drink tea at any hour, my sister will not touch anything but black coffee.
16. My old phone was dead by lunchtime, whereas this one keeps going until about Thursday on one charge.
Condition
17. If you leg it now, you might just catch the 8:05 to Manchester.
18. The app keeps your draft safe if the wifi cuts out on you halfway through a paragraph.
19. Unless the pitch is waterlogged again, the match goes ahead on Saturday.
20. You can borrow my laptop as long as it comes back with the charger by Friday.
21. Provided that nobody objects, we will start at nine and finish by lunch.
Place
22. Leave the car keys where you will actually see them in the morning.
23. Wherever we go on holiday, my dad finds the nearest bakery before we have even unpacked.
24. We plonked the picnic blanket where the big oak gave us a bit of shade.
Purpose
25. She stuck the cleaning rota on the fridge so that nobody could claim they had never seen it.
26. We left at seven so that we would not be circling the car park for half an hour.
27. Mr Okafor spoke slowly in order that the new students could follow along.
Manner
28. He went on about the trip as if he had planned every last detail himself.
29. Our dog cocked his head at me as though he understood every word about the vet.
Relative clauses
30. The nurse who patched up my son's knee after the trampoline disaster has worked on that ward for donkey's years.
31. My laptop, which my brother handed down to me in 2019, still opens everything I need, if slowly.
32. This is the lemon drizzle recipe that my aunt wrote out for me on the back of a gas bill.
33. Ravi, whose car conked out on the ring road yesterday, is working from his kitchen table today.
34. The little café that opened by the library last month already has a queue every morning.
Noun clauses
35. What she said at the end of the meeting caught everyone off guard.
36. I honestly do not know whether the hardware shop opens on Sundays.
37. The real problem is that nobody checked the postcode before booking the van.
Compound vs complex sentences (and compound-complex)
Watch what happens to this sentence when one word changes.
- Priya ran laps of the park every morning before school, and in March she won the county cross-country. That is compound. Chop it at and and you are left with two perfectly good sentences.
- Priya ran laps of the park every morning before school until she won the county cross-country in March. Now it is complex. Say until she won the county cross-country in March by itself and it falls flat, because it needs the first half.
That really is the whole difference. Compound and complex sound like two settings on the same washing machine, but the test is only whether each clause could survive alone. Towson University's guide to sentence types goes into more depth if you want it, and here are all four types side by side:
| Sentence type | What is in it | What glues it together | Example |
|---|---|---|---|
| Simple | One full clause | Nothing | The bus was late again. |
| Compound | Two or more full (independent) clauses | and, but, so, or, yet, for or nor (or a semicolon) | The bus was late again, so I walked in the drizzle. |
| Complex | A full clause and at least one dependent clause leaning on it | because, when, although, who, that and so on | I walked in the drizzle because the bus was late again. |
| Compound-complex | Two or more full clauses, plus at least one that leans | Both kinds of glue | I walked because the bus was late again, and I still got in before the boss. |
Compound-complex sentence examples
So what is a compound-complex sentence? It is a compound sentence with a dependent clause wedged in somewhere, which sounds fiddly until you notice how often you say them out loud. Three from a fairly ordinary week:
- When the power finally came back on, the fridge shuddered into life, and every clock in the kitchen started flashing 00:00.
- I meant to ring you, but my phone died before I could find your number.
- The bakery that does the good sourdough was shut, so we made do with a supermarket loaf.
How to write a complex sentence in 3 steps
- Start with your main idea as a plain, simple sentence. Ours was The shop closed early.
- Choose the little word that says how the ideas connect. A reason calls for because, timing for when, and a twist for although.
- Attach the clause and decide about the comma. We went with The shop closed early because the heating packed in. There is no comma, since the clause comes last.
If you are stuck for ways to grow a short sentence, a sentence expander can throw a few ideas at you. We gave TotBot's Sentence Expander The shop closed early. with a 20-word target, and this was the first thing it came back with:
The shop closed early today, much to the disappointment of several customers who had planned to make purchases.
That one is complex, by the way, and the dependent clause doing the work is who had planned to make purchases. The other two came back a lot wordier, roughly 40 words apiece over two short paragraphs, so our advice is to pick whichever one suits you and give it a quick tidy.
Complex does not mean complicated
In grammar, "complex" is about how a sentence is put together and nothing else. It tells you nothing about how hard the sentence is to read, which is why I left when it rained. counts as complex even though a child could read it without blinking.
The trouble starts when one sentence carries clause after clause after clause, because not everyone reading is a strong reader. In the 2023 adult skills survey by the US National Center for Education Statistics, 28% of US adults scored at Level 1 or below in literacy. In 2017 the figure was 19%.
To show what we mean, we wrote this 44-word monster. It is grammatically correct, and it is exhausting:
Although the meeting, which had already been moved twice because the manager who was supposed to lead it was travelling, finally started at noon, several people who had not seen the updated invitation arrived late, so the first item had to be discussed again.
Then we ran it through TotBot's tool to simplify complex sentences, and it came back as two sentences, 38 words in total:
The meeting, which had been rescheduled twice because the manager was traveling, finally started at noon. However, some people arrived late because they did not see the updated invitation, so the first item had to be discussed again.
Both are still complex sentences, notice. What changed is that each one now carries a single main idea instead of three, so you can read it in one breath. It did also swap travelling for traveling, the American spelling, so if you write British English you will want to change that back by hand.
4 mistakes that catch people out, and how to fix them
1. The dependent clause left out in the cold
Because the printer was broken. looks like a sentence at first glance, what with the capital letter and the full stop, but there is no main clause in it anywhere. As Purdue's guide puts it, "A dependent clause cannot be a sentence."
The fix is to give it something to lean on: Because the printer was broken, I emailed the file to reception instead.
2. Commas in the wrong place (or missing)
If you finish early you can head home needs a comma after early, and nobody has put one there. She smiled, when she saw the card has the opposite problem, with a comma that is just getting in the way.
The fix: if the clause opens the sentence, put a comma after it. If it closes the sentence, you usually do not need one.
3. Since or as with two meanings
Cambridge Dictionary notes that since can refer to a time or give a reason. Most of the time the context sorts it out for you, but not always, and Since Tom joined the team, sales have gone up could mean "from the time Tom joined" or "because Tom joined".
The fix: use because for a reason. For time, rephrase: Sales have gone up in the months since Tom joined.
4. The overloaded sentence
Every clause you bolt on asks the reader to juggle one more idea before they reach the full stop. The UK government's writing guidance has a handy rule of thumb here: "Try to split up sentences that are over 25 words long."
The fix: keep one main idea per sentence. A sentence shortener can have a go at trimming it. We fed TotBot's Sentence Shortener this 42-word sentence to see what it would do:
Because the parcel that we had been waiting for since Monday arrived after the office had closed, the driver, who did not have a key, left it by the back door, where it stayed until the cleaner found it the next morning.
It returned 22 words:
The parcel arrived after hours, so the driver left it by the back door, where the cleaner found it the next morning.
Much easier to read, yes, but notice that "since Monday" and the bit about the key have vanished. A shortener has no way of knowing which details your reader cares about, so it is worth checking what it cut. For more habits that slow readers down, have a look at our guide to common writing mistakes.
Quick quiz: which one is a complex sentence?
Here are eight to try, and a couple of them are sneaky, so do not rush. Label each one simple, compound, complex, compound-complex or fragment. The answers are just underneath.
- When the alarm rang.
- The alarm rang at six.
- The alarm rang, but nobody woke up.
- Nobody woke up when the alarm rang.
- Because the road was icy, the school opened late.
- I will wait until five.
- I will wait until you call.
- The book that you lent me was brilliant, and I finished it in a day.
Show the answersHide the answers
- Fragment. There is a subject and a verb, but nothing finishes the thought. What happened when the alarm rang?
- Simple. One clause, and at six is only a time.
- Compound. Both halves could stand alone, and but joins them.
- Complex. When the alarm rang hangs off the main clause and needs it.
- Complex. The because clause cannot stand alone, and it comes first, hence the comma.
- Simple. Did until fool you? Until five has no subject or verb, so it is a phrase rather than a clause.
- Complex. This time until is followed by a subject and a verb (you call), and that turns it into a clause.
- Compound-complex. Two full clauses joined by and, plus that you lent me tucked inside the first one.
FAQs
What are 5 examples of complex sentences?
Here are five from ordinary life. The bold part of each one is the dependent clause.
- We ended up eating in the garden because the sun finally came out at about four.
- When the phone rang at 3 a.m., I was convinced something terrible had happened.
- The roofer who fixed our gutter last spring left his ladder propped against the shed for a week.
- Although she was shaking like a leaf, my sister gave a cracking speech at the wedding.
- Give me a ring if the bus is late again tonight.
Can a sentence start with "because"?
Yes. Plenty of us were told at school never to do it, which was probably just a way to stop fragments. As long as a main clause turns up afterwards, you are fine: Because it was freezing, we lit the fire. Stop after Because it was freezing, though, and you have written a fragment.
Can a sentence have more than one dependent clause?
There is no official limit. When we got there, the hotel that we had booked was full has two (a when clause and a that clause), and you probably say sentences like it every week without thinking. The real limit is your reader. By the third or fourth clause they start losing the thread, so two is usually plenty.
Wrapping up
If you remember one thing from all this, make it the lean test. Every complex sentence has a clause that could stand alone and at least one that leans on it, and the leaning one usually starts with a word like because, although or when. Put that clause first and it gets a comma. Put it last and it usually does not.
When a draft starts to feel like wading through treacle, a sentence simplifier can break up the overloaded sentences. For padding there is a tool to shorten sentences, and there is one to make a sentence longer for the lines that feel thin. Whatever you use, read the result out loud afterwards. If it no longer says what you meant, put your version back.
Cheat sheet for the comma rules
| Kind of clause | When it comes first | When it comes last (usually) |
|---|---|---|
| Time, reason, condition, place, purpose or manner | Comma after it | No comma needed |
| Contrast (the although kind) | Comma after it | Comma before it |
| Which clause (extra detail) | Does not go first | Commas on both sides |
| That clause (the detail you need) | Does not go first | No commas at all |
Examples written by the TotBot team. Tool results are shown exactly as the tools produced them.
Sources: Purdue OWL, Identifying Independent and Dependent Clauses; Purdue OWL, That vs. Which; Troy University Writing Center, Dependent Clauses; USC Writing Center, Writing and Punctuating Complete Sentences; Towson University, Kinds of Sentences and Their Punctuation; Cambridge Dictionary, Until; Cambridge Dictionary, Since; GOV.UK, Clear language; US National Center for Education Statistics, PIAAC 2023 results.