Combining sentences: where two flat clauses become one.
Knowing the sentence types is one thing; fusing your own short clauses into one controlled complex sentence is the skill the grammar band actually rewards. Four moves do nearly all the work, and the trap is doing too much of them at once.
What this page is. Its sister page, sentence structure, names the four types. This one is about the move: taking the short, true-but-flat sentences you actually write and combining them into one sentence that carries the relationship between the ideas. That is what a range of complex structures means in the band descriptor, and it is the single most teachable lift from Band 6 to Band 7. Below: the four ways to combine, one idea climbing from Band 5 to Band 8, and ten to drill. One warning runs through all of it, range without control is not rewarded, so the goal is the cleanest combination, not the longest.
Four ways to fuse two clauses into one.
Start from two short, true sentences, the kind you already write, and combine them. There are really only four moves, listed here from the lowest-value to the highest. Each example shows the flat pair on the left and the combined version on the right.
Coordinate
clause + and / but / so + clause
Join two equal ideas with a coordinator (the FANBOYS: for, and, nor, but, or, yet, so). The easiest move and the lowest-value, the two ideas stay side by side as equals, so the grammar shows little about how they relate.
Costs fell. Access widened. → Costs fell, and access widened.
Subordinate
main clause + because / although / while… + clause
Make one clause depend on the other with a subordinator. This is the Band 7 workhorse: the join itself carries the logic, cause, contrast, condition or time, so the reader sees how the ideas connect.
The scheme cut staff. Access fell. → Access fell because the scheme cut staff.
Relativise
noun + who / which / that + clause
Fold a whole idea about a noun inside the sentence as a relative clause. It lets you add detail without starting a new sentence, and it is a clear marker of range.
The scheme launched in 2019. It cut costs. → The scheme, which launched in 2019, cut costs.
Reduce to a phrase
participle (-ing / -ed) or noun phrase + main clause
The most economical move, and the Band 8 one. Drop the subject and the verb be from a clause, leaving a participle or a noun phrase that leans on the main clause. Powerful, but the phrase must clearly attach to the right noun.
The scheme was launched in 2019. It cut costs. → Launched in 2019, the scheme cut costs.
The one rule that outranks all four: control, not length
The moves multiply, but stacking every one of them into a single sentence produces a tangle an examiner reads as poor control, not range, “Launched in 2019 to cut costs, the scheme, which was popular, although underfunded, succeeded because demand, which was high, persisted.” One or two clean embeddings per sentence is the target. And combining is not the same as joining with a comma: two independent clauses still need a real join, so “Costs fell, access widened” is a comma splice, not a combination. Reach for range once, then let the next sentence be short.
One idea, combined four ways.
Three flat sentences: The council built a new cycle lane. It wanted to reduce traffic. The lane quickly became popular. Watch the same idea climb as the moves are applied. Notice that the top of the climb is the shortest version, not the longest.
Band 5 · no combining
“The council built a new cycle lane. It wanted to reduce traffic. The lane quickly became popular.”
Three correct simple sentences, but the grammar shows nothing about how they relate. Clean, and capped.
Band 6 · coordinate
“The council built a new cycle lane to reduce traffic, and it quickly became popular.”
A purpose phrase (to reduce traffic) and a coordinator (and) pull the three into one. Correct, but the and is the lowest-value join, so it still reads a little like a list.
Band 7 · subordinate + relativise
“To reduce traffic, the council built a new cycle lane, which quickly became popular.”
The purpose is fronted and the third idea is folded in as a relative clause (which…). One controlled complex sentence, the structure now carrying the relationships.
Band 8+ · reduce to a phrase
“Built to ease congestion, the council’s new cycle lane quickly proved popular.”
The first two clauses are reduced to an opening participle phrase (Built to ease congestion) attached cleanly to the subject. The most economical version of all, and the shortest. Length fell; control rose.
Three traps that turn range back into error.
Combining is the lift, but each move has a way of misfiring. These three account for almost every combined sentence that loses marks. Spot the wrong version, then the fix.
| The trap | What it looks like | The fix |
|---|---|---|
| Over-stuffing (the tangle) | Although the lane, which cost millions, was built to cut traffic, it became popular, because demand was high. | Split it. One or two embeddings per sentence, then a short one. |
| The dangling phrase | Built in 2019, the council saw cycling rise. (The council was not built in 2019.) | The reduced phrase must attach to the right noun: Built in 2019, the lane… |
| The comma splice in disguise | The lane cut traffic, it became popular. (Two full clauses, only a comma.) | Use a real join: a subordinator, a relative clause, a semicolon, or two sentences. |
The pattern behind all three is the same: the ambition outran the control. When a combined sentence feels heavy, the answer is almost never a longer join, it is a full stop. More on relative clauses → · the four sentence types →
Ten to combine.
Each item gives you flat clauses and asks for the best controlled combination, not always the longest. Choose the version that shows range without losing control, then press Check answers for your score and the reason behind each one. Nothing is sent anywhere.
You can name the four moves in a minute. Reaching for the right one under timed pressure is the work.
Over-combined tangles and dangling phrases hide in your most ambitious sentences, exactly where you cannot catch them yourself.
In a lesson I mark your writing against the grammar criteria and show you, line by line, where two flat sentences could become one, or where an ambitious sentence has tangled. Lessons are £20 for fifty minutes, one to one, in proper British English; the first step is a free 25-minute introduction. This page is adapted from the grammar chapter of the forthcoming Ultimate Guide to IELTS Speaking.