Do any linguistics geeks reading have a word I can google for this phenomenon? That is, a word that means something like "a word or phrase that is bidirectional in one language but part of a unidirectional pair in another"
You can use lent and borrowed in both directions (I lent X to him; he lent X to me -- I borrowed X from him; he borrowed X from me) so the main difference is not in whether the verbs can be used bidirectionally, but in how you indicate the direction.
I suspect Spanish (and maybe Polish) disambiguate in different ways, but disambiguate I'm sure they do!
Those are both unidirectional: lent is always “the (possibly implicit) direct object moves from the subject to the indirect object prefaced with ‘to’” while borrowed is always “the (possibly implicit) direct object moves to the subject from the indirect object prefaced with ‘from’”.
Birectional would be where the subject could be the source or recipient depending on, e.g., the preposition used to relate the other party as the indirect object.
idk if there are regional exceptions, but in general borrow and lend seem more akin to learn and teach, respectively. The have an implicit direction: (from, in the case of borrow; to in the case of lend).
I teached something from you today or I will learn you calculus in extracurricular classes don't work.
In Spanish it is disambiguated in a similar way as you were mentioning (to me, to you)
"Alquilo" translates literally to rent, so not really the same:
- Me alquilas un piso. (you rent me a flat)
- Te alquilo un piso. (I rent you a flat)
I think a better translation to borrow/lend is "prestar/dejar:
- Me prestas/dejas un lápiz. (you lend me a pencil/I borrow a pencil from you)
- Te presto/dejo un lápiz. (I lend you a pencil/You borrow a pencil from me)
Language is interesting!