Rafe usually gets his homework done (in a matter of minutes) at aftercare. The exceptions are reading homework (English on Thursdays, Japanese over the weekend), where he has to read to us, and one variety of Japanese writing homework where I'm supposed to test him. I think LSA could do that one, but either they don't, or he'd rather do it with me.
Today, exceptionally, he had some math homework to do at home. It involved finding 3D objects with faces matching various polygons, tracing those faces, and then labeling them. We pretty quickly resorted to the tangram pieces, and while Rafe was playing with them, he named the parallelogram in Japanese: 平行四辺形. I said parallelogram out loud (referring to the same piece) and then asked Rafe if 平行四辺形 meant parallelogram. He said yes, with confidence, so later I asked him how he knew that 平行四辺形 and parallelogram meant the same thing. He explained that in his classroom, there's a poster with the names of different shapes on it. I asked which language, and he said in Japanese. So I asked if someone had told him that 平行四辺形 and parallelogram mean the same thing. He said, no. So I asked how he knew what a parallelogram was. He said because *I* had just said so.
I was really curious about the internal structure of 平行四辺形, since it was clearly (from the length of the word and shape of the syllables) written with many kanji. I had already guessed 四 (four) and 形 (shape). It turns out that 平行 means parallel and 四辺形 means four-sided shape.
A bit later, working on the hexagon, he asked me:
Mom, why don't they just make it 六角 (rokkaku)?
me: Because 六角 (rokkaku) means six-corners, 六角形 (rokkakkei) means six corner shape.
Rafe: Yeah, but then there's 三角 (sankaku, three-corner, 'triangle'), 四角 (yonkaku, four-corner 'square') ...
He's got a point there! Checking the dictionary online, I see that 四角 is actually pronounced shikaku, not yonkaku as he said it, and 六角 (rokkaku, six corner) does mean 'hexagon'. Maybe
the longer form is more common for hexagon, or maybe the teachers like using it because it ends with the same 'shape' morpheme as things like 平行四辺形.
When Toby got home from baseball, I asked him if he knew what the pieces of 平行四辺形 meant. He knew that 平行 means parallel and guessed that 四辺形 had something to do with four and shape.