soweli is not like animal in English- it doesn't refer to any kind of animal, just to a collection of creatures with sufficiently similar traits (mammals + marsupials being a large majority of that)
What traits?
That's harder to answer bc the category has grown out of many examples. I would say the most common traits are:
But this list is not exhaustive either.
Also, a creature can have only some of these and still be considered soweli (such as the platypus).
You can have overlapping traits and be in multiple categories (also the platypus, living often in the water, is sometimes considered kala).
And you can have many soweli traits but still be mostly considered kala (dolphins, whales, seals) due to having more kala traits. These might also be in multiple categories, depending on who you ask.
The categories operate based on feeling, and those feelings happen to include a list of traits common to each category, but the feeling of a creature is most important.
Bats are mammals, and animals, but they are not soweli. They have leathery skin, so some speakers consider them akesi. They fly, so many speakers consider them waso. They can be quite small, which some speakers will consider small enough to be pipi.
So the better question to ask is, what does a creature feel like to you, and to your listener? Use that information to express what you're thinking of!
There's a related discussion about what a noka/luka is, which I'll keep short with my favorite example from my own nasin, in addition to counter-examples
I consider the wings of a bird to be noka, because they are locomotive limbs. Some people consider them luka, because they are anatomically analogous to arms (i.e. in the same part of the torso)
I consider the claws+feet of a bird to be luka when they are used to grab things, and I consider them noka when they are used for walking or standing. Some people consider them only noka because they're the only obvious standing limbs on a bird, and others consider them only noka because of anatomical analogy.
Again, feeling is important.
Interesting - so words are relative to the definitions of the conversation partners moreso than in English.
That's my experience, yes- I strive to consider the meanings of words to my conversational partner, and this lets me better understand them and them better understand me.
Fwiw, I think this applies just as much to English too- we just don't think about it as often. Maybe because the definitions of English words are more specific, so we assume others are operating on the same specific definition? And that is correct often enough to not come up