How do you say 'are you single' in German?

You are the one:

"Du bist der Eine" (for a male)

"Du bist die Eine" (female)

You are the only one:

"Du bist der Einzige" is the phrase used when addressing a male.

"Du bist die Einzige" is the phrase used when addressing a female.

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Du bist die Eine????????? No, no, no, whilst it is a verbatim translation of each Word it is definitely not something a native German speaker would say.

The correct translation of you are the one is Du bist derjenige/diejenige, e.g.

You are the one (who did it) - Du bist derjenige/diejenige (m/f), (der/die es getan hat)

You are the one (for me) - Du bist derjenige/diejenige (für mich)

The formal form is Sie sind derjenige/diejenige