Funny but I thought I had been using a scope tag here like on other SE sites I use but it seems not to exist after all.
We do have an on-topic tag but I don't think this is great since discussions of what's on-topic invariably also go into what's off topic.
I think the lead tag for this trio should be scope with two synonyms on-topic and off-topic both redirecting to it.
For those of you who are programmers you can think of it this way. What makes a better name for a variable: big
, small
, or size
?