The haiku is finished at seventeen morae — a standing thing, lacking nothing. It is also the first three phrases of the waka, the opening of a larger whole that has not been written yet. Self-sufficient at one scale; a proper part at the next.
This is the seed of nesting. Not a fragment promoted to a poem, but a poem that was always also a beginning. Keep this — every later move depends on a unit that can be both done and not-done at once.
The waka is the larger whole: 5·7·5·7·7. The haiku is its upper phrase; the closing 7·7 is the answer — the human turn the haiku left for the reader to supply, now supplied. Containment runs vertical: haiku ⊂ waka. The first stroke of the figure.
Nothing here overlaps yet. This is pure hierarchy — a thing inside a larger copy of its own kind. The vertical line, drawn from the seed upward to the frame that holds it.
At the center sits the pivot — and a waka's hinge always sits at its center, the third phrase that turns the upper into the lower. Here the turn is the figure itself: ⊥. Nesting is the vertical; the chain-to-come is the horizontal. They seemed to contradict — containment versus overlap — but the contradiction was an artifact of forcing both onto one axis.
Rotate one ninety degrees and it dissolves. They never had to be each other. They only had to meet at a single shared node. The ⊥ is that meeting — one junction, two perpendicular strokes.
The horizontal stroke is the chain. In the renga, each verse is used twice: it closes the poem behind it and opens the poem ahead of it. One tooth, two pairings — and the two readings are sealed from each other, so the same syllables carry a different sense each way. A love-letter looking back becomes a teaching looking forward.
This is the zipper: shared unit, two directions, meaning shifting by position. Drawn flat, left to right — the second stroke, crossing the first at the junction.
Now stand at the junction node and look at what lives there. It is a haiku — complete at its own scale. It is a prefix — the vertical opening of the waka above it. It is a tooth — the horizontal share of the chain through it. One object doing three jobs at once, exactly where the strokes of the ⊥ cross. That is the wedding: not three things laid near each other, but a single node carrying all three roles.
And it is not rare poetry. It is the wavelet, the skip-list, the two-edge graph — every structure that must be whole, nested, and shared at the same time, losing nothing at the seam. The renga is only the oldest place the three were fused in one tooth.