Both 怎么 and 怎样(怎么样) are used to ask questions. In some sentences, they are interchangeable, while in some others only one of them can be used. In this post, we analyse the differences of these two pronouns.
1. When asking the manner in which an action is carried out, we can use both 怎么 and 怎样.
Example 1. 我怎样/怎么去酒店？ [phr] How can I get to the hotel?
2. When asking for a reason, we can only use 怎么.
Example 2. 你怎么不穿鞋就出来了？ [phr] Why did you come out without your shoes?
3. When expressing a surprised tone, we can only use 怎么. And it has to appear independently in a sentence.
Example 3. 怎么，你现在就得走？ [phr] What? You have to go now?
4. When asking for the opinion of the interlocutor, we can only use 怎么样 at the end of a suggestion. 怎么样 is usually separated from the rest of the sentence.
Example 4. 明天一起去游泳吧，怎么样？ [phr] Tomorrow let's go swimming together. What do you think?
5. When forming a rhetorical question, we only use 怎么.
Example 5. 您帮了我这么大的忙，我怎么能不感激您呢？ [phr] (with respect) You have done me such a big favour. How could I not be grateful to you?
6. When asking for a situation, a condition, or the nature of someone/something, we use both 怎么 and 怎么样 but certain conditions exist in the position of the word in the sentence.
Only 怎样／怎么样 can appear in the position of a predicate (6a) or a complement (6b):
E.g. 6a 今天天气怎么样？ [phr] How is the weather today?
E.g. 6b 昨天你考得怎么样？ [phr] How was your exam yesterday?
Both 怎么 and 怎么样 can be used in the position of an attributive modifier, but there are different requirements on formats: (6c, 6d)
E.g.6c 她是一个怎样的人？/ 她是怎样的一个人？
When forming a question asking for the general situation, we only use 怎么:
E.g. 6e 怎么了？ [phr] What's the matter? What's wrong?