The waka is a type of Japanese poem form consisting of a 5-7-5-7-7 syllable structure. The poet is generally expected to divide waka into two distinct sections, usually signified in English by a hard stop of some kind, such as a period or semi-colon. This division is between the first three lines and the final couplet.
Sedoka is a Japanese poem form consisting of two tercets that each have a 5-7-7 or sometimes 5-7-5 syllable structure. There’s quite a bit of disagreement among western sources as to what theming the poem is intended to have, but natural imagery and a concept of reflective thinking do seem to appear consistently.