Preverbs don't only indicate direction, quite often their main role is to make the verb perfective:
- "Bemegyünk az épületbe." -- We enter the building. We end up inside of it.
- "Megyünk az épületbe." -- We are moving towards the building with the intention to enter it, but it's unclear if we will succeed or not.
- "Belépünk az épületbe." -- Again, we end up inside of the building.
- "Lépünk az épületbe." -- This sentence isn't too probable to be honest. It's supposed to mean something like "we are in the process of stepping into the building", but I personally would use the preverb in this meaning too.
In negative this difference is less clear, but I recommend following the same pattern, so if you'd use the preverb in a positive sentence, use it in its negative equivalent as well.
Thanks for the clear explanation. As far as I know, Hungarian does not have a perfect tense. The perfect tense has a connotation of fulfillment. Does this mean that we translate the prefixes in the past as follows:
Léptem az épületbe: I enter the building
Beléptem az épületbe: I have entered the building
I know this question should come later (with the fel- preverb), but I am not there yet and it is sticking in my head.
The expression for: going to the airport is: megy a repülőtérre. Does that mean that: felmegy a repülőtérre is the only way to address that the airport is above? So that the translations would be:
Megyek a repülőtérre: I am going to the airport
Felmegyek a repülőtérre: I am going up to the airport
And how would one say: I am going up to the bus, as that would already be: felszállok a buszra? Would that be: felszállok a fölötti buszra? Or felszállok fölött a buszra?