熱 - Four Little Flames Means It's Too Hot To Touch

Readings & Meanings:

あつ（−い） heat, hot (TO THE TOUCH)

ねつ fever, heat, hot, craze

Common Usage:

熱

熱心

Examples:

熱が高いときは消化が悪くなるので、食べ物は無理に食べさせないでください。
(From a PDF on children's fevers, can't link to it: www.kcif.or.jp/jp/benri/medhical-PDF/10-3.pdf)

野口英世はアフリカで熱心に黄熱病の研究し、それが為に命を落とした。

Translations:

Because digestion is hard when the fever is high, do not uselessly force (the child) to eat.

Hideyo Noguchi passionately studied yellow fever; due to that, however, he lost his life.

Bonus:

Wait a minute, there's a bunch of other kanji in this kanji! There's 土, there's 丸, and there's 火.

What, you don't see 火? Well... you're right. It's not exactly 火. It's called "rekka" and it's the little dots of flame under the rest of 熱. It's a radical, and it belongs to the "hi" or flame group.

Other kanji with rekka: 点　、然

Important:

Remember that radical I discussed above? Use it to remember that this 熱い has to do with hot things, like water and food. Think of this 熱い as a result of using a gas stove to heat up your dinner.

Also, think of touching the four flames under 熱. Ouch! That's hot to the touch, right?

References:

http://www.jlptstudy.com/2/index.html
Easy Kanji, by Fujihiko Kaneda (Amazon Link)
JapanesePod101.com
http://www.thejapanesepage.com/kanji/kanji/a.htm