Learn Dutch: Er start plotseling een motor. - An engine suddenly starts.

When a Dutch sentence has an indefinite subject (a subject with een instead of de or het), it rarely sits at the very beginning. Dutch prefers to use er as a dummy subject in the first position to introduce the new information, pushing the real subject (een motor) further back.

Is er considered the actual subject of the sentence?

It acts as a grammatical placeholder, but the verb still has to match the real subject. Here, een motor is singular, so the verb is start. If it were multiple engines, the sentence would be Er starten plotseling motoren, changing the verb to plural to match the real subject.

Could I start the sentence with the word plotseling instead?

Yes! If you want to emphasize the suddenness, you can put plotseling in the first position. Because of the verb-second rule, the verb comes next, followed by er and then the real subject: Plotseling start er een motor.

Why does the adverb plotseling come before een motor?

In sentences that use er to introduce a new subject, adverbs describing time or manner (like plotseling) usually go right after the verb and before the indefinite subject.