Breakdown of Minä annan heijastimen teille molemmille.
minä
I
te
you (plural/formal)
antaa
to give
molemmat
both (of them)
Questions & Answers about Minä annan heijastimen teille molemmille.
Why are both teille and molemmille in the allative case?
In Finnish, when a personal pronoun is paired with a quantifier like molemmat (both) or kaikki (all), both words must agree in case. Since you are giving the reflector to them, the allative case is required for both the pronoun (teille) and the quantifier (molemmille).
Why is the object heijastimen in the genitive-looking accusative case instead of the partitive?
The verb antaa (to give) implies a completed action where the entire object is transferred. Because the sentence has a subject (Minä) and expresses a complete action, the total object takes the genitive-accusative ending -n. If you were giving an unspecified amount of an uncountable substance, you would use the partitive.
Could I just say annan heijastimen molemmille and leave out teille?
Yes, but it changes the meaning. Molemmille alone just means 'to both' or 'to both of them' depending on the context. Including teille explicitly clarifies that you mean 'to both of you'.
Since there are two people receiving it, shouldn't heijastimen be in the plural?