As if and as though mean the same. They are used to say what a situation seems like. It looks as if/as though it is going to rain.
To show that a comparison is unreal, we use a past tense with a present meaning after as if/as though.
- She looks as if/as though she is rich. (Perhaps she is rich.)
- She looks as if/as though she was rich. (She is not rich.)
In a formal style, were can be used instead of was to show that a comparison is unreal.
- She looks as if she were rich.
Note that we do not use a past perfect for a past unreal comparison.
- She looked as if she was rich, but she wasn’t. (NOT — as if she had been rich.
In an informal style, like is often used instead of as if/as though. This is common in American English.
- It looks like it is going to rain.