～階
～かい · ～kai · JLPT N5 · noun
building
🏢 kai sounds like sky: each kai is one floor closer to the sky
階 has the hill radical 阝 (stepped ground) plus 皆 (kai, all), which gives the sound. Stepped levels = floors. Note 3階 is often sangai, and 1, 6, 8, 10 contract: ikkai, rokkai, hakkai, jukkai.