The Japanese word for floor is
床

ゆか - yuka

Japanese Definition

floor
1. 名詞. 床ゆか
2. 名詞. 階、フロア
用法
道路などに面した階は、どの英語圏においてもground floor、その上の階は、英国英語圏（インド、香港等も含む）を除くと、second floor（2階）となり、上昇に従いそのまま階数が足されるが、英国英語圏ではfirst floorとなり、そこから加算されるため、second floorは日本語で言う3階にあたり、それ以上の階は日本語などと、1階ずつずれることとなる。米国英語等
mezzanine floor, mezzanine
3. 名詞. （海・湖などの）底そこ
4. 名詞. 議院席
5. 名詞. 発言権
6. 名詞. 底値そこね
7. 動詞. 床をはる
8. 動詞. うちのめす
9. 動詞. 閉口させる

床
1. n. the floor (the bottom surface of a room)
床を掃く - to sweep the floor
2. n. a bed
3. n. (theater) a raised area of a stage where a presenter or musician sits
4. n. a raised platform erected along the Kamo River in Kyōto in summer, used as an outdoor tea shop or restaurant
5. n. a raised platform roughly 30cm tall used in dirt-floored rooms as a seat
6. n. a raised area on which to sleep: a bed
7. n. a sickbed
8. n. the floor
9. n. tatami mats
10. n. the seat of an oxcart
11. n. short for 床間 / 床の間: an alcove with a raised floor along one wall of a traditional Japanese living room
12. n. an alcove with a raised floor used as a study: see 付書院
13. n. a box seat, such as at a parade, theater, or stadium
14. n. short for 床店: a stall with a raised floor used as a store
15. n. short for 床屋: a barbershop, from how such shops were historically often tokomise
16. n. short for 床船梁, 舵床: the large wooden beam at the very aft of a traditional wood-hulled Japanese ship, upon which the rudder is seated
17. n. the heel of a plough; the part of the bottom of a plough that touches the ground and guides the ploughshare
18. n. short for 苗床: a seedbed
19. n. short for 鉄床, 金床: an anvil
20. n. sickbed
21. counter. beds

階
1. affix. step; stair; storey
2. affix. class; rank; level
3. counter. floors, storeys (of a building)
（私の）オフィスは五階にあります。 - (My) office is on the fifth floor.