The Japanese word for fire is
火

ひ - hi

Japanese Definition

fire
1. 名詞. (不可算)　火ひ、炎ほのお、火炎。
2. 名詞. (可算) 火が熾ること。熾った火。
3. 名詞. (不可算　錬金術)　四大元素の一つ。
4. 名詞. (可算)　火事、火災。
There was a fire at the school last night and the whole place burned down.
During hot and dry summers many fires in forests are caused by regardlessly discarded cigarette butts.
5. 名詞. (可算)　(英) 暖房器具。
6. 動詞. 他動詞: ～に火をつける。
7. 動詞. 他動詞: （銃などで）～を撃つ。
8. 動詞. 他動詞: ～を解雇する。
9. 動詞. 他動詞: （陶器など）～を焼く。
10. 動詞. 自動詞: （銃などを）撃つ。
11. 動詞. 自動詞 (生理学): （細胞内の機能を）活性化する。

首を切る
1. (I) fire (to terminate the employment of)
2. to fire, to terminate the employment of

火
1. n. a fire:
2. n. a flame
3. n. : (synonyms, ja, 火気, tr=kaki, ファイア, tr2=faia, 炎, tr3=honō)
4. n. cooking fire
5. n. a firestarter
6. n. sparks
7. n. light (matches or lighter)
8. n. : (ja-x, 火を貸してもらえる？, ひをかしてもらえる？, Can I borrow a light?)
9. n. heat
10. n. : (synonyms, ja, 火熱, tr=kanetsu, 熱, tr2=netsu)
11. n. a conflagration
12. n. : (synonyms, ja, 火災, tr=kasai, 火事, tr2=kaji)
13. n. a signal fire
14. n. : (synonyms, ja, 狼煙, tr=noroshi)
15. n. (by extension) a light
16. n. a burning passion
17. n. menstruation
(synonyms, ja, 月経, tr=gekkei)
18. n. a fire
19. n. one of the five classical elements in traditional Chinese philosophy and medicine: see (pedia, Wu Xing)
20. n. (historical) under the old 律令 system of ancient Japan, a military grouping, consisting of 10 soldiers: a squad
(synonyms, ja, 分隊, tr=buntai)
21. affix. fire
22. affix. light
23. affix. burning
24. affix. passion
25. affix. imminently
26. affix. explosive

撃つ
1. v. to fire a weapon
銃を撃つ、核を撃つ、ミサイルを撃つ - to fire a gun; to drop a nuclear bomb; to launch a missile

火事
1. n. a fire (damaging occurrence of fire)
2. n. (dialectal Kagoshima) a fire (damaging occurrence of fire)

炎
1. n. a flame
ハリー・ポッターと炎のゴブレット - Harry Potter and the Goblet of Fire
燃え広がる炎 - Catching Fire
2. n. (figuratively) an intense emotion, passion
3. n. a flame
4. n. (figuratively) an intense emotion, passion
5. suffix. (medicine) -itis, inflammation of...
6. affix. flame, blaze
7. affix. burning
8. affix. firehot, red-hot
9. affix. *
10. affix. flame, blaze
11. affix. (figurative) passion, emotion

火災
1. n. fire, conflagration (as in a disaster)
2. n. (Buddhism) one of the three major calamities that destroy the world

ストーブ
1. n. heater, stove
2. n. (attn, ja, TODO: appliance used to heat rooms)

暖炉
1. n. hearth, fireplace (open recess in a wall at the base of a chimney)

囲炉裏
1. n. a traditional sunken hearth or fireplace cut in the middle of a floor; usually found in homes in northern Japan
(synonyms, ja, 炉, tr=ro, ゆるり, tr2=yururi)

Dictionary entries from Wiktionary