The word "why": what's the difference between 为什么 and 怎么? In Mandarin, usually 为什么 is used to express "why". Sometimes 怎么 is also used to mean the same thing.

What makes them different? Most grammar books I beleive introduce 为什么, but I feel many Chinese use 怎么 on WeChat. Since 怎么 also means "what" or "how", sometimes I got stuck to understand what it means on a context.

Also, is there any other words to mean "why", except them and 为何 (which is the same as 为什么 but literary, right?) and 为啥...?
什么 = what

怎= how

怎么 = how / how is that (how come)

为什么 = for what = why

为什 is short form of 为什么

为何 is the literary form of 为什么

何故 or 何以 is the literary form of 什么原因 or 什么导致 (for what reason = why)


Examples:

&quot;什么我不能去？&quot; = &quot;What? I can't go?&quot; or &quot;what (you mean) I can't go&quot;
&quot;怎么我不能去?&quot; = &quot;How is that I can't go?&quot; or &quot; how (come) I can't go?&quot;
&quot;为什么我不能去?&quot; = &quot;For what (reason) I can't go?&quot; or &quot; why I can't go&quot;

Basically 为什么 (why) emphasizes the reason itself ; 怎么(how is that) emphasizes 'in what manner' or 'with what method'  the cause exist