ASK A QUESTION How do you know when to use the article El vs Un
I have just finished lesson 1.3 on SpanishDict
How do you know when to use the article El vs Un (or La vs Una for feminine)? for a noun
For example. We say el queso for cheese not un queso
Leave the cheese alone.
I am going to eat a piece of cheese.
Is that what you are asking?
There are cases where Spanish requires an article, but English doesn't, or vice-versa, but I can't think right now of a situation where English would use "the" and Spanish "un", or the other way around. The general logic of these two articles (definite and indefinite) is the same in both languages. Would you say "I have bought the dog" if I had no clue about what dog you are talking about? The same applies to Spanish.
The reason why vocabulary lists tend to say "El queso" is just so you can learn the gender along with the word, not because the article has a special function there.