Spanish prepositions
Prepositions are words that express relationships between two words (usually spatial or temporal).
de - from / of
en - in / on / at
El abuelo es de España. El abuelo está en Nueva York. (The grandfather is from Spain. The grandfather is in New York.) Notice the use of ser and estar. Since de implies origin, we will always use it with ser. Since en implies location, we will always use it with estar.
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Interleaving
Drilling one topic until it feels easy is tempting, but mixing different topics together builds more flexible, durable knowledge. The variety forces your brain to work harder, and that's what makes it last.