Koji

In one fell swoop, I had occasion to marvel the sheer complexity of this language and despair of ever learning it properly.

The (spoken) word koji (こうじ) can mean any of the following, depending on the context. These are all pronounced exactly the same!

• 工事: construction; probably the most common definition, and the only one I was familiar with.
• 公示: announcement; likely just as common, but I'd never heard it before.
• 好餌: easy prey; an odd phrase in English, but this is not English. The kanji are, effectively, the one's you would expect. Probably uncommon.
• 小路: a small road; again, the kanji suggest the meaning, though the pronunciation is irregular.
• 後事: one's future affairs; useful enough, I guess.
  
• 高次: meta-; as in, for example, meta-linguistics.
• 好事: the definition in my dictionary only includes the English saying "There's many a slip between the cup and the lip," which I don't even understand. And, my favorite:
• 麹: simply, bafflingly, the definition is "koji."