"We are in the big house."
Translation:Wir sind im großen Haus.
The way I remember it is if the direct object is declined from normal (e.g. der or das changed to dem) then the weak inflection is used and en is added to the adjective.
If the subject is stationary (dormant) then the word "in" forces dative. If it is moving toward the object (active) then "in" forces accusative.
In this example, the subject is dormant, forcing the dative case. The dative case changes das Haus to dem Haus which then requires a weak inflection for "groß".
Thus, the sentence becomes, "Wir sind in dem großen Haus" which contracts to, "Wir sind im großen Haus".
Could someone please explain how "Wir sind im den großen Haus" is incorrect? (If I incorrectly used den, I understand. But my understanding of this sentence was that an article - whether den/die/das/der/etc. - should be placed before "großen Haus".) Still scratching my head over dative and whatnot :D
The dative does not deal with movement, accusative does. I.e. if you going into the house from the outside you would use accusative. Whereas, if you are already in the house (and staying there) the dative is required.
In this sentence "Im" is a contraction of in and dem. So in the sentence above the article does come before "großen Haus" it's just formed part of im.
( This is my understanding anyway)