Questions & Answers about Il gatto è dentro la casa.
Why isn't there an extra little word after dentro, like we do with vicino a?
Can I use in instead of dentro here?
You could say Il gatto è in casa, but they give slightly different feelings. Dentro strongly emphasizes the physical position of being enclosed or specifically inside the structure. In casa is more like saying the cat is indoors or at home.
Will dentro ever change its ending to match the noun?
No. Because dentro is a preposition of place here, its ending never changes. It stays exactly the same whether it describes one masculine cat or ten feminine cars.