1. He came back after a week.
2. He came back in a week.
3. He will be back after a week.
4. He will be back in a week.
[Which onea are incorrect? What abe the differences?]
In these sentences, “in” seems to mean “within” — meaning before a full week.
In these sentences, “after” means 8 days or more.
Out of the given sentences, all of them are grammatically correct. However, there are slight differences in their meaning:
1. "He came back after a week." This sentence means that the person returned one week later from a reference point.
2. "He came back in a week." This sentence implies that the person returned within the duration of a week. It suggests that the person came back sometime during that specific week.
3. "He will be back after a week." This sentence indicates a future event. It means that the person will return one week later from a reference point in the future.
4. "He will be back in a week." Similar to sentence 3, this sentence also refers to a future event. It means the person will return within the duration of a week, sometime during that specific week.
In summary, the differences lie in the tenses used and the specific interpretations of "after" and "in." The distinction between "after" and "in" is subtle and can vary based on context and personal usage.