"Por la noche" is a phrase, and can not be translated 'word for word' so to speak. In Spanish, there are two words for 'for'-- one being 'por', and the other, 'para'. They each have their own set of rules and must be used accordingly. To say 'for the night', it is necessary to say 'para la noche' instead of using 'por'.
A very helpful guide I've found to help with por and para is: http://www.studyspanish.com/lessons/porpara.htm
Good luck and hope this helps!
Based on the info from the link given I believe this is classification for why "por" is used in this case:
Rule: to express an undetermined, or general time, meaning “during” Model: Se puede ver las estrellas por la noche.
The sentence isn't expressing exactly when she at night she reads just that she does in general.
Spanish (unlike English) is a regulated language.
The official regulating authority is the, Real Academia Española (Royal Spanish Academy)
The website is http://www.rae.es
This is a great wiki at http://en.m.wikipedia.org/wiki/
Here's a little blurb from the wiki about the RAE.
Real Academia Española The Real Academia Española (English: Royal Spanish Academy), generally abbreviated as RAE, is the official royal institution responsible for overseeing the Spanish language. It is based in Madrid, Spain, but is affiliated with national language academies in twenty-one other hispanophone (Spanish-speaking) nations through the Association of Spanish Language Academies. The RAE's emblem is a fiery crucible, and its motto is "Limpia, fija y da esplendor" ("[it] cleans, sets, and casts splendour").
@LauritaPepita - The drop down menu...
Hola Laurita. You have discovered a fundamental problem with duo. The drop down menu at best may contain the right choice for the answer in a given exercise sentence.
In some cases, like yours, the correct answer is not listed at all because the word you are peeking at is part of a fixed phrase or expression.
Like "los sábados" becomes "on Saturdays". In this case we are left to puzzle out that "por la noche" is a phrase that means "at night".
It will be great when duo can actually teach phrases. But until then the comment section plays a critical role in looking for hints.
Yes, some are probably meant to be silly. They are most accurate tho it seems to me when introducing a new word. Lots of the words sound new the third time round because I didn't study Spanish when I was very young. Children would just soak it up. Still I feel I love learning here.
That's strange, the sentence doesn't even make sense "the woman reads 'as' night". I put "at" which made the most sense to me even though I thought "por" meant "for" (which in some cases I think it does). Though if "at" is correct it seems like "by" should also be right considering that they both convey the same meaning in this instance.
'a' in Spanish is often used in the way English speakers use 'to' (yo voy a la ciudad = I go to the city). Granted, when telling the time they use 'a las diez' (at 10 o'clock).
In this phrase 'por la noche' means 'at night'.
Some phrases you just have to learn - a direct 'to English' translation doesn't always work. I've seen a lot of people on DL get frustrated with some phrases but it is what it is ... be thankful you're not learning English (that's got far more exceptions and special cases).
I thought the same, because to look THROUGH the window is mirar (in the required conjugated form) POR la ventana. But for parts of the day the phrase por la is used. Por ejemplo: mañana por la mañana = tomorrow morning, mañana por la tarde = tomorrow afternoon, mañana por la noche = tomorrow night. One last example Trabajo por la noche. = I work at night.