As far as I understand, 世界 means world or the world.
And these two words 世间 and 世界上, I think they both mean the same: in the world. But I am not sure if I interpret them correctly.
Is there any difference between these two words 世间 and 世界上?
世间 specifically refers to 人世间 (human's world)
世界 generally refers to a world or all worlds, for example
彿家有提及三千大千世界 - Buddhism mentions three thousand worlds
火星是一个冰冷而没有生命的世界 - Mars is a cold and lifeless world
童话世界中的人物 - Characters in the fairy tale world
世界 cannot be replaced by 世间 in any sentence above
When we mention 世间上 or 世界上, both referring to the human world, but 世界上 sounds more colloquial and 世间上 sounds more literary
Example:
世界上竟然有这么不怕死的人
世间上竟有如此不畏死之人
Both mean "There is actually such a person in the world who is not afraid of death" but the first one is more colloquial and the second one is more literary
notice: 世上 can be short for 世界上 or 世间上
世上, 世界上 , 世间上, 世间 and 人世间 they all mean the same 'The human world`.
世间 = 人間, the place on earth we (living people) live.
世界, world, the earth round, the place occupied by all beings.
In the broader view, they mean the same, but in the narrower view, 世间 implies a definite space we (the living beings) live on, while 世界 is more general, or vague.
间 - a room, or a space, 世间 (人间,陽间) the place on earth we (the living beings) live; the opposing space is 陰间 (a place the dead lives).
界 - boundary, the realm, which includes 上界(天界, a place god lives), 下界(地界, a place the living beings live), and 陰界 (the place the ghost lives).
Because of the slight difference, sometimes one cannot replaces the other. For example:
世间(上)商人多陰險狡詐 shouldn't be replaced by 世界(上)商人多陰險狡詐.
And, 世界各國...shouldn't be replaced by 世间各國...
This answer can be confusing, but, hey, just writing for fun :)
They might have the same meaning, but do have different usage nowadays.
the world around people / in one's life
It focuses on people or human and express in an emotional way.
这世间每天有许多事发生 means lots happening around you (or in your life).
Also often used in chinese literary works (or classic style literature), and feels odd with 世界.
世间所有的相遇，都是久别重逢, all encounters in life are reunions after a long time.
time and space (on earth or in novel)
It appears more objective and can be used in academic or formal writing.
世界上有成千上万的生物, millions of creatures living in the world
吉尼斯世界记录, Guinness World Records
魔戒发生在中土世界, The Lord of the Rings happened in Middle-earth
Although they both have the same meaning, 世间 is a more proper noun than 世界上.
For example, between I'm sorry and My apology, 世间 has equivalent formality as My apology.
世间 is used in writing, whereas 世界上 is used in speaking.
They share the same meaning.
