It's reflexive when used for learning something. Like, 'I learn Swedish' would be Jag lär mig svenska, 'You learn Swedish' is Du lär dig svenska, and so on.
English has verbs like that too! "Let me help (meaning assist) you" versus "I can't help (meaning stop or prevent) it."
Lease (rent from/rent to), consult (give/receive advice), clip and hew and cleave (cut apart/join together), dust (cover with fine particles or clean them away)... I could give out a bunch more examples, but I think my time and your patience would give out long before you read them all. :)
In English there is also an old-style construction -- to learn me = to teach me. When you see it written it's usually written to indicate dialect, i.e., "Mama is gonna larn me [learn me] my ABCs."
You can see it as "lär" means "teach" and that there is no verb for "learn". Therefore, to say that you are learning something, you can say that you teach yourself (lär dig).
in the german language, which hat a big influence on the swedish lanuage, "to teach" is "lehren" and " to learn" is "lernen".
i guess in swedish you can also use "jag läser" for " i learn". but this again can be used as "i read". in german that would be "ich lese"...
pretty mixed up huh? but i guess i confused you more now.. :D
Yes, but if you use "undervisar" you have to say "i svenska", since i is the preposition to be used with undervisar.
in this case the order would be as "varför undervisar du honom i svennska?"