"A mouse is eating a sandwich."
Translation:En mus spiser en sandwich.
How should you know when to use "en" or "et" for "a" and "an" in a sentence ?
"En" and "et" does not correspond to the English articles "a" and "an." Danish nouns have two genders, and the indefinite article ("en" or "et") depends on this. If it is an en-word, then the article "en" is used. If it is an et-word, then the article "et" is used. You have to memorise the gender as you learn the word because there are rules later on which will also depend on their respective genders.
English does not have this, so most learners are thrown off when they start learning the language (at least I was).
So...which is for which gender and how do you tell which word is which gender?
There's no easy way. You'll have to learn the gender as you learn the word.
The same thing in Latin. there are genders. I took a full year of latin at my school.
So genders of words need to be memorized, i get that. I know a bit of Spanish and that's similar. But which one corresponds to which gender? Et=masculine, and en=feminine, or vice versa?