They pass a kid of maybe fourteen halfway down the stairs.

"Woah, what's that?"

"Recursively nonpublic."

"Garbage. I mean, uh, I'm super curious and frustrated."

"I've heard swearing before, kiddo."

"All my coworkers cuss and I'm trying not to get in the habit. Good skill with your secret stuff."

"Very sensible of you. Goodbye?"

"Goodbye."

They get down the stairs and into the air shaft at the center of the building. It has a red maple tree (currently green), some planters of flowers, and the abandoned chalk drawings of the building's small children.

"Recursively nonpublic!" says Petal. Quite possibly while the kid is still in earshot.

The kids stares back, then shakes his head and moves on.

Ari starts naming the things in the courtyard, including using the flowers to explain what it means for something to be a subtype of something else.

This is so interesting! Also Petal harvests the maple tree and puts the resulting seed on top of Ari's head.

Ari smiles and says, "That might fall off," but makes no attempt to remove it. Instead she goes into explaining the concept behind "might," using the example of a pebble that she might throw into one of the planters but might miss.

After the vocabulary has been sufficiently explained, Petal echoes, "Might fall off!" and retrieves the seed, holding it telekinetically next to her body in what seems to be her favourite way to carry objects.

Ari should sew Petal a tiny shoulder bag. And line it with tinfoil so seeds can't get stuck in it. It would be both practical and adorable.

More language! More questions about what Petal could make! Digression into the difference between"might" and "can"!

That's a pretty fine distinction and she has trouble picking it up but she gives it her best effort.

It's okay if she doesn't super get it; it's a tricky question. Could she make any parts of this plant? Could she make any parts of that plant? Could she make one of this wood chip? Could she make one of that rock?

Petal scrunches up her tiny face in an expression of deep concentration, then floats up with her maple seed to the tree she got it from.

"Petal make seed," she says. "Make seed... tree. Make tree no; make seed! Make...? Make no? Tree?? Make-no tree??"

"You can make the seed that will grow into a plant but can't make grown-up plants?"

"Noooo," she says. "Make-no tree." She goes up to the tree and gently rustles it in a visibly exaggerated imitation of the way she interacts with things when she's harvesting from them. "Make-no tree, make tree seed." She goes up to a small bush and rustles it next. "Make-no plant, make plant seed." A different plant, rustle rustle. "Make-no flower, make flower seed. What's-that?? What's-that make-no??"

"Things you didn't make? Hmm . . ." Normal? Regular? Alive? "Natural?"

"Noooo..."

Think think think.

Okay, how about...

She deposits the seed on the floor. "Put seed. What's-that? Put."

She picks it up, goes to the tree, rustles the tree, carries the seed away from it. "Make seed. What's-that? Make."

She floats up to Ari and peers dramatically at her with lots of exaggerated eye movements. "Look Ari. What's-that? Look."

An exaggerated nibble from a leaf. "Eat plant. What's-that? Eat."

She picks up the seed again, goes to the tree, rustles demonstratively, produces the seed once again. "Make-no tree?? Natural tree?? Eat tree?? Sleep tree?? Whurbl tree??? What's-that??"

"Ohhhh! Make, eat, put, sleep, are verbs. Petal, tree, leaf, seed are nouns."

"Verbs! Petal want verb! Petal make seed tree, verb seed make. Petal make seed tree, verb tree what's-that??"

"Trees make seeds and Petal makes seeds. Trees make seeds that grow into trees. . . . Does Petal make seeds that grow into trees?"

Tiny face-scrunch of deep thought.

"...put seed Ari," she says, depositing the seed on Ari's head. Picking it up again, "Put-no seed Ari. Verb seed Ari?"

And for another example, "put seed floor," depositing the seed on the ground. Picking it up again, "put-no seed floor. Verb seed floor?"

"Put-no is pick up. Pick up is the opposite of put." It's really amazing to watch both how smart Petal is and how little language exposure they have. Human babies spend a while not being able to deliberately pronounce words at all, so they have a lot more receptive exposure before trying to produce anything. It's almost like Petal was born knowing a language and is learning Convergentlanguage as a second one while still very much in her critical period.

"Opposite!" she says delightedly. "Put seed floor," she does that, "pick-up seed floor!" and that. "Opposite!"

Okay, now for the main event. She goes back to the tree. She balances the seed on a branch. "Put seed tree." Removes the seed from the branch. "Pick-up seed tree." Exaggeratedly rustles the tree and produces the seed from it by sleight of, er, telekinesis. "Make seed tree. Verb tree? Make tree no; make seed. Verb tree. What's-that verb??"

"You made* the seed from the tree!" She's honestly surprised Petal even realized there was a gap there, and tries to remember any cases where Ari has used prepositions when doing example complete sentences. She's no linguist, but she's pretty sure other languages do prepositions differently.

Maybe she should start taking that "born knowing a language" hypothesis seriously; it's bizzare but it wouldn't be the weirdest thing about Petal by a long shot.

"'From' and 'tree' and 'put' are words. Ari knows 'from' and 'tree' and 'put'. Petal knows 'from' and 'tree' and 'put'. Words Petal knows Ari does not know?"

*Translator's note: it only looks like Ari is cavalierly using irregular verbs all the time with no effort to explain them. Convergentlanguage has vanishingly few irregular verbs, especially compared to English.

"Make seed from tree," she agrees. "Make-from tree? Petal can make-from tree, can make seed from tree? Can make-from plant, can make seed from plant? Can make-from Petal no, can make-from Ari no. Can make-from rock yes. Make thing from rock, see thing, know word thing."

"There is no word for make-from because only you can do it. Ari cannot make-from, Plasma cannot make-from, Petal can make-from. So the word is whatever Petal wants!"

"Make-from," she declares. "Word make-from."

"An excellent word!" And sufficiently different from the word ordering in e.g. 'jam is made from fruit and sugar' that no-one will be confused. "You can make-from rock? I'm surprised; I didn't know."