This is the 109th most frequent Polish word.
świecie
"Świecie" in English means "world" (locative case) or "light" (vocative case).
The word 'świecie' is the locative form of 'świat' (world), used here to indicate the place where something happens.
Witaj na tym pięknym świecie.
Welcome to this beautiful world.
Here, 'świecie' again is in its locative form, employed to denote the general scope or location of described phenomena.
W całym świecie roście wiele różnych roślin.
In the whole world, many different plants grow.
In this sentence, 'świecie' emphasizes the characteristics of the described world context, used poetically to illustrate feelings.