Baseball is a team sport where each side has nine players. （定语从句。where 为关系副词）

Weddings are where two peoples get married.（表语从句。where 为融合型关系副词，等于places where） 

【网友注意】千万不要认为：定语从句用where 引导，其先行词一定是place 之类的名词！有些不表示地点的名词，也完全可以使用where 引导的定语从句修饰。例如，先行词从“明显地点”到“模糊地点”。例如：situation（情况，情形）, case（情况）, point（地步）, stage（地步）, book（书本）, story（故事）, trick（把戏）, play（戏剧）, film（电影），sport（体育运动），wedding（婚礼） 等。举例如下：

Can you think of a situation where this idiom can be used? 你能想出一个使用这个成语的情况吗?

I have heard of a case where a soldier riding a bus did not offer his seat to a woman with a baby. 我听说这样一个情况，有个士兵坐车，一位妇女抱着娃娃他不让座。

Noise is coming to the point where we can't put up with it. 噪音快到我们无法忍受的地步。

The mature trader arrives at a stage where most trading actions have become nearly automatic. 成熟的交易者能达到这个地步，大多数交易行为几乎是自动的。

Your face is like a book where people may read strange matters. 您的脸正像一本书，人们可以从那上面读到奇怪的事情。

This was a film where Spielberg used real actors instead of toys.

在这部电影中,他使用了真正的演员,而不是玩具。

关于where 引导的各种从句，举例说明：

1. I wonder where their wedding will take place. （宾语从句）

2. Their wedding will take place where they got acquainted.（状语从句）

3. Their wedding will take place in a village where they got acquainted.（定语从句）

4. A wedding is where two people gets married.（表语从句）

5. A wedding is a place where two people gets married.（定语从句）