Turning down an invitation: grammar question


**Turning down an invitation**

For some reason I got it into my head that `すみませんがちょっと` was a way to turn down
an invitation.

But for example say you were asked to do X at time Y, and you want to do X but
time Y doesn't work for you. You can say `よじはちょっと`: in this case "4 o' clock
is a little bit inconvenient".

Why does one use the particle が and the other the particle は? Or am I just
completely incorrect and it should be `すみませんはちょっと` all along?




This が does not denote the subject here, instead it means "but". "I'm sorry,
but ... (insert reason, or leave it unsaid which is most common)".

For the latter case, "4 o'clock" is the topic, which is why は is used. すみませんは
is never correct, unless you want to say something completely different.




This が does not denote the subject here, instead it means "but". "I'm sorry,
but ... (insert reason, or leave it unsaid which is most common)".

For the latter case, "4 o'clock" is the topic, which is why は is used. すみませんは
is never correct, unless you want to say something completely different.

