Use of "the" before proper nouns.

[Bak2DFuture]

I am a native English speaker and am fluent in the language, and almost invariably know the correct way to say things. Having said that, I note I could have "said that" in a simpler way. Never mind..................the point being I know what to say but often do not know why.

I am trying to teach an advanced Chinese student English and fill in her gaps wherever I find them.

Point : I was telling her to-day that we say, " say hello to a teddy bear" but " say hello to Teddy Bear". In other words, we do not precede proper nouns by "the".

My student immediately pointed out that we had just done exactly that :

1. We went to the Olympic Games

and,

2. We crossed the Amazon river.

Can anyone throw together a few [hopefully] rules that circumscribe this issue succinctly?

[Mister Micawber]

There are no rules, only guidelines. And there are whole books on the subject. Most bodies of water, island groups, deserts, ships, some countries, hotels, newspapers, mountain ranges, etc, etc take the definite article. Others do not.
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Native English teacher at Mister Micawber's

[Haihao]

I would suppose:

1. The utterance is based on an imaginative set of sport games {World Cup, WBC, Olympic Games, ...}. When we take one specific member out of the set, the is utilized for the purpose of +identification against the other mambers of the set. Cf. We went to the movies. Cf. We went to the sea.

Another example:

When earth is taken as a unique entity regardless of other planets, Earth is a proper noun used without the, whereas the Eerth is uttered in regard to its membership of the universe or set {Mars, Moon, Eerth, ...}.

2. the Amazon river: common noun river is involved, modified, and identified. BTW, same hypothesis applicable too: {A river, B river, Amazon river, ...}.

Just my two cents.

Best regards