More often than not I come across a sentence structure like this:
Upon arrival, I learned that she was not in the town.
But if I change it this way, does it change the meaning?
Upon arrival, I came to know that she was not in the town.
Furthermore, as oerkelens came up with a good point (more common?)
Upon arrival, I found out that she was not in the town.
The Question:
Is learn preferred if it's news? Or something which is noesis? I thought of several examples and could replace learned with came to know in almost all cases (of course, except learned a lesson). Is there any instance wherein "I learned that…" cannot be replaced by "I came to know that…"
My understanding: As I said, I think learn is more common when it's news that you did not expect. On the other hand, I came to know is less surprising and subconsciously known to us as a second option. Furthermore, I found out… is something that comes after you putting some efforts.
Having said this, If you learn that she's not in the town, it's the news and bit surprising whereas If you come to know that she's not in the town, it's okay without any surprising element. You, though subconsciously, knew the possibility of the second option of her being not in the town. If you found out that she's not in the town, you made some efforts to learn/know the news.
Note: I'm particular about putting the word that in the sentences in question. Or else, I learned… and I came to know… are two different things, it's clear to me.
Best Answer
There's some nuanced differences between the two. I came to know implies a more lengthy, substantial or involved process of acquiring knowledge than I learned. Synonyms of come to know include come to understand and become acquainted with, which are a little more distant from learn. For example, I came to know calculus suggests a drawn out process or a deeper, more personal relationship with the subject than I learned.
I don't know of any instances where I learned cannot be validly replaced by I came to know, but I do know that the exchange doesn't always work in the other direction. I came to know my neighbor is fine, but I learned my neighbor is unsemantic (people are not facts or ideas; you cannot learn them). I discount learned a lesson here because it carries a very specific meaning and uses learn in a different sense than usual. Cambridge even lists it as a phrasal verb (or at least thinks it merits a separate entry).
However, your question includes that after both phrases. Having that makes it about some particular pieces of information. In this case, came to know is a superset of learned, because both are completed processes of acquiring knowledge, and learning is about retaining specific facts. Because of this, I can't think of any cases where one works and the other doesn't if you include that.
Regarding your example, what's the context? Was the discovery of this information expedient and easy? Is the sentence intended to be merely informational? If so, use learned. Was it very difficult or time consuming to find out the woman's status? Is it the knowledge extremely important and worth emphasizing? Are you trying to avoid being prosaic? If so, use came to know. Compare: