"What is the meaning of this Kanji?" Our teacher highlighted two Chinese characters on the sheet being projected to the screen in front of us. One looked a bit like a flower. The other, like a child's climbing frame.

"らいねん," we volunteered as a class. "Next year."
来年 rai-nen.

"And this one?"

The flower was still there but the climbing frame had been replaced by a broken ladder with the bottom-most rung twisted free.

"らいげつ," we replied. "Next month."
来月 rai-getsu.

"How about this one?"

Again, the same flower but now alongside a small chest of drawers.

"らいにち," we started confidently and then paused. "… next day?"
来日 rai-nichi.

"In this case," our teacher explained. "日 (nichi) is understood as if it were 日本 (nihon), Japan. So it means: 'coming to Japan'."

There was a silence as we took this in.

"…. why doesn't it mean 'next day'…?" asked someone at last.
a.k.a. Defend your language, Japanese person!

Our teacher paused. "Well, what is the Japanese for 'next day' or tomorrow?"

"あした," we all chorused.
明日　ashita.

"Yes. That's why."
a.k.a. Silence, you foreigners!

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(Note: らいねん, らいげつ, らいにち and あした are written in the phonetic Japanese script, hiragana.)