Comparative for user defined type?

I have the following code:

Size is a kind of value. The sizes are tiny, little, midsized, big and huge. A thing has a size. Definition: A thing is large if its size is big or more.
It gives the following error:

Problem. You gave as a definition 'A thing is large if its size is big or more'  : but that definition is wrongly phrased, assuming it was meant to be a grading adjective like 'Definition: a container is large if its carrying capacity is 10 or more.'

Am I doing something wrong, or is it just impossible to define comparatives based on enumerated values?
Enumerated values can be compared (“the size of A is greater than the size of B”), so it seems like it should be possible to define the comparative (and have “A is larger than B”).

Many thanks!

Seems like it’s impossible, although as you say, there’s no obvious reason why it should be.

Looks like this wording works:

Definition: A thing is large if the size of it is at least big.

That defines “large”, but not “larger” / “largest”.

Thanks!

I ended up simulating “to be larger/smaller than” as verbs implying (or reverse implying) the same conditional relation, and "the largest/smallest " as two separate (and rather wordy) phrases that work through the full logic.

Not very elegant, but will hold the fort until a better solution is created/discovered.