熱 means 'fever' (ねつ) but also means 'hot', as in 熱い (あつい). Like how having a high temperature is a sign of having a fever.
Also, just the kanji 情 and 熱 on their own both have 'passion' as one of their meanings. If the question was just "passion", it would be hard not to pick this answer! :P
November 25, 2014 at 3:15am