appointment

It would be more natural for me to say 'I have to meet a friend' though I'd probably just say 'Sorry, I don't have time.'

Thank you~

Do you think it's impossible to have 'appointments' with friends, and appointments must be formal?

Thank you~

I'd love to. But ...

(they smile , exeunt)

No, thank you.

No need to say why - a simple no, thank you is all.

Thank you~

One of them street survey people stopped me once and asked me if I'd like to come into a room above a pub where they had their computers, so I went out of curiosity.
About a dozen people were there who they'd pulled off the street and we had to sit at the computers pressing keys for about 20 minutes as questions kept coming up on screen like "Do you eat chocolate products", "Which ones?", "Rate this list of 10 products in order of preference" etc etc.
It was a complete and impossible shambles so I just kept pressing random keys and giving nonsensical jokey replies.
At the end of it we were thanked and given a pen and pencil set as a reward, ha ha!

Yes, since about 1850 approximately. You really must try to find some more modern reading matter.

Thank you~

If someone, you parents say, asks you what you're going to do this evening, and you have to meet you friends, which is pre-arranged, what would you say?:

?I've arranged to see my friends.?

Other ways?

I'm goin' out with ... .

I'm meeting ... .

Me and ... are (doing STH).

You could say that, or you might say "I'm going to see my friends", or name them e.g. "I'm going to see John, Mary and Peter". In informal speech native speakers usually do not say more than is needed, and it is understood that the meeting of friends was 'arranged'.

Thank you~