German has two kinds of joining word, and they do opposite things to the word order. Getting this wrong is the single most audible mistake a learner makes, and the fix is a list of about twelve words.
The two groups
Coordinating conjunctions join two clauses and change nothing. There are five that matter:
und (and), aber (but), oder (or), denn (because), sondern (but rather).
Ich arbeite heute, aber ich bin müde. — I am working today, but I am tired.
The verb bin stays in second position exactly as it would alone.
Subordinating conjunctions send the verb of their own clause to the very end.
Ich bin müde, weil ich heute arbeite. — I am tired because I am working today.
arbeite has moved from second position to last. That is the whole difference.
The list worth learning
| Word | Means |
|---|---|
| weil | because |
| dass | that |
| wenn | if, when (repeatable) |
| als | when (one past event) |
| ob | whether |
| obwohl | although |
| damit | so that |
| bevor | before |
| nachdem | after |
| während | while |
| seit / seitdem | since |
| bis | until |
| falls | in case |
| solange | as long as |
Every one of these sends the verb to the end. There are no exceptions in the list.
denn and weil mean the same thing and behave differently
This pair is worth its own note, because both translate as "because".
Ich bleibe zu Hause, denn ich bin krank.
Ich bleibe zu Hause, weil ich krank bin.
Same meaning. denn is coordinating and leaves the verb alone; weil is subordinating and sends it to the end. In speech, weil is far more common.
Two verbs at the end
If the clause already has a verb at the end — a modal, a perfect tense — the conjugated verb goes behind it.
Ich weiß, dass er nicht kommen kann. — I know that he cannot come.
Ich weiß, dass er nicht gekommen ist. — I know that he did not come.
In a main clause it would be er kann nicht kommen and er ist nicht gekommen. In a subordinate clause the finite verb hops to the very end, behind the infinitive or participle.
Putting the subordinate clause first
You can lead with the subordinate clause. When you do, the whole clause counts as the first element, so the main verb comes immediately after the comma.
Weil ich krank bin, bleibe ich zu Hause.
bleibe comes before ich, because the subordinate clause has already used up first position. This is the verb-second rule doing exactly what it always does — see German word order.
A comma is not optional here. German still separates every subordinate clause with a comma, including before dass and weil, where English dropped its comma decades ago.
wenn or als
Both mean "when", and they split by how many times the thing happened.
| Use | For | Example |
|---|---|---|
| wenn | present, future, or repeated past | Wenn ich Zeit habe, lese ich. |
| als | a single completed past event | Als ich Kind war, wohnte ich in Berlin. |
If it happened once in the past, it is als. Every other "when" is wenn.
What to actually memorise
The fourteen-word list, and the habit of dropping the verb to the end whenever one of them appears. Once that is automatic, the two-verbs-at-the-end case and the front-loaded clause both follow from it without needing separate rules.
Rules stick faster once you have met the words. Every example above links to its own page.
Practise in the trainer