Active: The children are learning Toki Pona.
Passive: Toki Pona is being learnt by the children.
Causative: The parent is teaching the children Toki Pona. (i.e. "makes them learn")
jan pi toki pona o,
Outside of pu, I have observed forms like *"pana sona" instead of "pana e sona" (to teach).
- mama li pana e sona pi toki pona tawa jan lili. (The parent is teaching Toki Pona to the children.)
→ *mama li pana sona e toki pona tawa jan lili.
It reads well (for an English-speaker), but it's not pu. The root for this seems to be that Toki Pona doesn't have a causative, and no passive. Otherwise a sentence expressing "The parent is making Toki Pona something known to the children" might have emerged. But such a sentence seems not to be possible because it would look like this:
- *mama li sona e toki pona tawa jan lili. *(The parent knows Toki Pona according to the children.)
The reason for this seems to be how pu shows how to "convert any verb into a noun" (pu, page 26):
- toki (something that you speak)
moku (something that you eat)
So *"ijo toki" (something to speak, something talkable) and *"ijo moku" (something to eat, something edible) turn into "toki" and "moku". The implicit rule seems to be that "ijo" is omitted before a transitive verb (*"ijo sona" → "sona") which prevents us from forming passives and causatives. I hope this "rule" can be interpreted like this, though: "ijo" is omitted before transitive verbs (like "toki" and "moku") except when used in order to express passives and causatives. Here's what I mean:
- nimi sin li ijo toki. (The new words are being spoken.)
kili li ijo moku. (The fruit is being eaten.)
toki pona li ijo sona. (Toki pona is being known.)
- mama li ijo toki e nimi sin tawa jan lili. (The parent makes the children say the new words.)
mama li ijo moku e kili tawa jan lili. (The parent makes the child eat the fruit.)
mama li ijo sona e toki pona tawa jan lili. (The parent teaches Toki Pona to the children.)
This is not a "pona" style, but it seems possible.