By all means give me a few technical terms without explaining them and I can look them up for myself.
I think there is no need for technical terms.
Bywać means to visit regulary, to occur sometimes or be in some state from time to time, while
być is something pernament.
On bywa w tym pubie co piątek.
Raz bywa zielony, raz czerwony w zależności od temperatury.Of course one can use here
być as well, the sense would be the same, however the frequency won't be so emphasized:
On jest w tym pubie co piątek.
Raz jest zielony, raz czerwony w zależności od temperatury.However in below examples there is a huge difference in meaning:
Liście są zielone. - a pernament state
Liście bywają żółte. -
not pernament state or
exceptions occur (they change their color from time to time or some species are yellow and can be found among green ones)
Further examples:
- "expetions that occur"
Liście L.capleinea (an invented by me name of a plant for purpose of this example)
są zazwyczaj zielone, aczkolwiek bywają też żółte w zależności od zróżnicowania osobniczego (sounds like a scientific bełkot, hehe) - should be read that "leafs of L.capleinea are usually green, but some of them might be yellow according to diversity found among specimen".
- "not pernament state"
Liście L.capleinea bywają czerwone jedynie późną jesienią - should be read "the leafs of L.capleinea are red only in late autumn, while in others season they have different colour (so there is a frequnet change during the year, hence no pernament state)