I've only known her... yesterday: for, ago, since?

When referring to the time frame of knowing a person, it can be tricky to choose the appropriate preposition. In the sentence "I've only known her... yesterday," we need to decide whether to use "for," "ago," or "since." Let's take a look at each one and how it changes the meaning of the sentence.

For

Using "for" in this context would result in the sentence "I've only known her for yesterday." This doesn't really make sense because "for" usually implies a duration that has passed. We use "for" to talk about a period of time in the past that has since elapsed. For example, "I've known her for five years." But "yesterday" is a specific moment in time, not a duration. Therefore, "for" doesn't work here.

Ago

Using "ago" in this context would result in the sentence "I've only known her yesterday ago." This sounds closer to what we're trying to say - that the speaker only recently met the person in question. But "ago" implies that "yesterday" is in the past, which is true, but it's not the main point of the sentence. The sentence is trying to convey the idea that the speaker's knowledge of the person is very recent, not that yesterday was in the past. So "ago" doesn't quite hit the mark either.

Since

Using "since" in this context would result in the sentence "I've only known her since yesterday." This preposition works the best because "since" is used to talk about a point in time in the past up until the present moment. It implies a more recent event or occurrence than "for," and it doesn't suggest that "yesterday" is in the past, which is not the main point of the sentence. "Since" also conveys the idea that the speaker's knowledge of the person is very new and recent, which is what we're trying to say.

In conclusion, the most appropriate preposition to use in the sentence "I've only known her... yesterday" is "since." This preposition conveys the idea that the speaker's knowledge of the person is very recent and new.