As if and as though are both used to make comparisons and introduce hypothetical scenarios in formal writing. The main difference between the two is that “as if” is more commonly used and considered slightly more formal than “as though.”

When using “as if,” the clause following it is often based on hypothetical or unreal situations. For example, “She looked at me as if she had seen a ghost.” On the other hand, “as though” is used to describe something that may not be true but seems possible or true. For example, “He ran as though he were being chased.”

In formal writing, both expressions are considered correct, but it is important to maintain consistency in your use of either “as if” or “as though” within a piece of writing. Additionally, some style guides suggest that “as if” is more widely accepted in formal writing compared to “as though.”

Overall, when choosing between “as if” and “as though” in a formal context, consider the tone and nuance you wish to convey. “As if” might be preferred for a slightly more assertive or formal tone, while “as though” may introduce a subtle nuance of uncertainty or possibility.