"The sister is in the city; the mother is at home."
Translation:Soror in urbe est, mater domi est.
Someone (Draconis) posted a mnemonic on Latin stackexchange: "cities, towns, islands smaller than Rhodes, and domus and rus", noting that it was incomplete, as it lacked "humus" and "focus". (https://latin.stackexchange.com/questions/4626/which-common-nouns-have-a-locative)
From time to time I've looked for a complete list of nouns that take the locative, without success, so I'm putting together my own.
domus (house): https://latin.cactus2000.de/noun/shownoun_en.php?n=domus
focus (hearth): https://enacademic.com/dic.nsf/enwiki/44617
humus (ground): http://www.lingvalatina.com/p/latin-mnemonics.html
mīlitia (military service): http://dcc.dickinson.edu/cicero-de-imperio/48
rūs (farm, countryside): http://dcc.dickinson.edu/grammar/latin/3rd-declension-locative-case
Albert Hoefer has a long list, but I'm sceptical of many of them (some look like adverbs (or ablatives of time within which), others look wrong for other reasons), but if you're interested (and can read German),
LOCATIVE is a case-form of a proper noun ( = name) of a city, town, or SMALL island ( = an island with only one city or town: coextensive with that city or town), to indicate "location IN" that place.
A few other nouns, listed elsewhere on this page (and domus , "home", is an important one in Duolingo), also have a locative form.
All other nouns, such as the nouns "city" (urbs) and "town" (oppidum), use preposition in + the ablative case to express the "location in" function.
Locative-case endings differ (naturally) according to the noun's declension.
Hope that helps.
Correct. This is a feature only for NAMES of cities, towns, small islands.
And if you use the noun "city" in conjunction with the city name, the locative is suppressed:
They are staying in the city (of) Rome: In urbe Rōmā manent .
(Notice that Rōmā is ABLATIVE, in apposition to the noun urbe , the ablative object of preposition in .)
But: Rōmae manent . "They are staying in Rome." In the absence of the noun "city," we use the locative.
I think Latin likes to "compress" where possible (= leave out unnecessary words), so I would expect "Soror est in urbe, māter domī" (with only 1 appearance of "est").
Or maybe: Soror in urbe, domī māter est. (with juxtaposition of the two locations, for better contrast; and the verb appearing just once)
Without the in it seems like you are trying to say "the sister is a city" or "the city is a sister". (But with a typo/error urbe in that case needs to be urbs, the nominative)
You need the in just like in English. I guess domi has confused you (it might have been wise for duo to add this later, because now everyone thinks it's the rule rather than the exception.) It's a special case that has a locative em case. Sorry for the double use of case haha
I'm not sure I understand the question.
But one rule of thumb is, when there's a nominative already (like māter or soror in this sentence) in the sentence, you (obviously) don't need to add a subject like "he, she, it." We wouldn't say The mother, she is in the house or whatever; just, The mother is in the house .