Spanish language Q&A Forum

Is there a rule for using the definite article in Spanish? It often trips me up. It doesn’t always follow the same pattern as English, eg in Castles text: …visitar castillos (no ‘los’, where in English there would be no ‘the’), but then:… la historia de los castillos medievales (in the  English version there is no ‘the’, the history of medieval castles; the history of the medieval castles is not incorrect it just has a different meaning).  Maybe, as in English, it’s very much about common usage and there’s no absolute rule.?

Could this be ¨no puedo dejar de pensar en ella¨ ?

Thanks

¿Tiene un bolígrafo?Do you have a pen? (formal you)

From the sentence, I think it means he/she has a pen. Why would it become do you have a pen?

Correct me please in the video below at 10:00 she says, Se te olvido el nombre. The name forgot you? 

Is this a way of accidental as well, something accidently forgot itself to you?  

https://www.youtube.com/watch?v=zI19K0Zv8m0&ab_channel=EasySpanish

Could you please elaborate more on which condition to use feminine or masculine? For example, why not a lo francés, since it's a style, and why not a ciegos, but a ciegas? Thank you!

In the example Nosotros podemos salir antes del trabajo temprano hoy, wouldn't it mean the same thing to say Nosotros podemos salir del trabajo temprano hoy.

In the quiz to find out which level you are, I was marked wrong for putting "hay" instead of "tiene" in the question about the city having a pool. Why is it giving me two different answers now? 

Puedo decir,  “para conocer a uno de mis actores preferidos”, también?