Learn Dutch: Deze plaats is vrij.

While plaats literally means "place" or "space," it is commonly used in Dutch to refer to an available seat on public transport, in a theater, or at a cafe. You could use stoel (chair), but plaats is the most natural word for a spot to sit in these situations.

Why do we use deze instead of dit for "this"?

We use deze because plaats is a de-word (de plaats). In Dutch, you use deze (this) and die (that) for de-words, but you must use dit (this) and dat (that) for het-words.

Does vrij mean the seat doesn't cost any money?

No, in this context, vrij means "unoccupied" or "available". If you want to say something is "free of charge" and costs zero money, you must use the word gratis.

How would I use this sentence to ask someone if a seat is taken?

You can turn this statement into a question simply by swapping the verb and the subject: Is deze plaats vrij? This is the standard, polite way to ask if you can sit somewhere.