though and although哪个不能放句首？

1.两词同义并可换用，但although语气较重，通常放在句首并用于正式场合。如：

I'd quite like to go out, (al)though it is a bit late. 我很想外出，虽然为时稍晚。

Although it was snowing, it was not very cold. 虽然下着雪，但并不很冷。

2.用though 时，可将强调的词前置，但although 不能。as也有此种倒装结构。如：

Poor though / as he is , he is happy.虽然他穷，但过得很愉快。

Child though / as she was, the actress was drawing a crowd. 尽管还是个孩子，这个女演员却引起了人们的注目。（child前无冠词a）

3. although 引导从句常指事实，而though 引导的句子可表假设。如：

Let's start as arranged though it rains tomorrow. 即使明天下雨，咱们也按预定的计划出发吧。（假设）

He was not unhappy although he had to live alone. 虽然得一个人生活，他毫无不快之感。（事实）

4.although 只用作连词，而though 除作连词外，还可用作副词，常置句末，句子较长时，也置于句中。如：

It's hard work, I enjoy it though. 这是苦差事，可我干得颇有乐趣。

There's no excuse, though , for hurting her feelings. 伤到她的感情一事，还是不可原谅。

5.though 可用于even though, as though 等结构，although则不能。如：

Even though I fail, I'll keep on trying. 我纵然失败，仍会继续尝试下去。

You look as though (=as if ) you know each other. 看起来你们好像彼此认识。

6. although 和 though 用作连词时不能和but连用，但可跟yet, still 等连用。如：

Although he lives alone, yet he is happy. = He lives alone, but he is happy. 他虽然单独生活，但很愉快。

7.though 常用于省略句。如：Though (he is) alone, he is happy.

一、用作连词 表示“虽然”，两者大致同义，可换用，只是 although 比 though 更为正式;

二、用作副词 although 一般不用作副词，而 though 可用作副词，且一般放在句末(不放在句首)，意为“可是”、“不过”.

都可以啊