Comparing "genju" and "ju"

The main differences between 根据 (gēn jù) and 据 (jù) are in how 据 is specifically used.

据 can be used with a single monosyllabic noun, 根据 cannot be used this way

Basically,据 can be used with single character words, while 根据 has to use words with at least two characters or more.

• 据 实 报道
• 根据 实 报道
• 根据 事实 报道

据 can be used together with certain words, 根据 cannot be used this way

据 can be used with together with 说, 闻, 悉, 传, 根据 cannot. These set two-character phrases are often used in formal and written Chinese, especially in news reports.

• 据说 他 去 上海 了。
• 根据说 他 去 上海 了。
• 据传 首相 将要 辞职。
• 根据传 首相 将要 辞职。

据 is often used with people directly

据 is often used while referring to people. Often it is used with "某人说" or "某人看来", just substitute that 某人 with the person you are refering to (or you can also refer to yourself）. If you use 根据, you need to use that person's name along with a noun phrase.

Examples

• 据 他 说，灾情 并 不是 很 严重。
• 根据 他的 说法，灾情 并 不是 很 严重。
• 据 我 看来，他 是 个 很 负 责任 的 人。
• 根据我的 看法，他 是 个 很 负 责任 的 人。

Sources and further reading

Books

• 现代汉语八百词(P.229) →buy
• 卓越汉语－公司实战篇 (p. 29) →buy

HSK6