Sorry, this seat's taken.

• You are travelling in Britain...and decide to take the train.
• You want to sit down... so you ask: 'Do you mind if I sit here?'
• The other person replies: 'sorry, this seat's taken.'
• This means, 'someone is sitting here: he isn't here right now, but, believe me, he's coming back.'
• Sorry. Sorry? It's not his fault you can't find a seat.. why is he sorry?
• However, in English we say this a lot. It's polite.
• It's a passive sentence: to be + past participle.
• This seat is + taken. (Take / took / taken - it's an irregular verb.)

This sentence is an example of tourism, tourism, public transport, public transport, public transport, public transport, passive voice (get), irregular verbs.