Tú Mandatos
I have encountered a phrase relative to construction of tú mandatos that i do not understand. I am to construct such a command from "dárselas al cartero" - give them (the letters) to the mail carrier. I do not understand why the verb dar is in the reflexive form, how "se" fits into the command or how to use "se" in this case.
2 Answers
Well, in the first place, "dárselas" is not in a command form (at least not in the spoken language, although you may find infinitive commands in written Spanish like recipes, instruction manuals, etc.), but rather an infinitive form. If it were in a tú command form it would be "dáselas". Next, "dar" is not in the reflexive form. In this case, "le" is the indirect object pronoun referring to "el cartero" and "las" is the direct object pronoun referring to "las cartas". In Spanish, when two pronouns that start with "l" are connected the first one changes to "se".
So, to add to pescador1's excellent explanation, in your specific example:
Dárselas al cartero (Give them [the letters] to the mailman). You would build an imperative command as:
Dáselas al cartero (if the command is being given to a "tú" pronoun form) or
Dádselas al cartero (you plural informal .... vosotros)
Dénselas al cartero (you plural formal.... ustedes)
I hope this helps!