Greek κόσμοι (kosmoi), singular kosmos; Latin mundi
Worlds, or ordered systems like our own. Because atoms and space are infinite, there are infinitely many worlds, some like ours and some unlike it, constantly forming and dissolving; Epicureans expected life elsewhere in the universe.
1. Key Texts
Now it is not to be thought at all likely, when there is an infinity of empty space in every direction and countless seeds flying through the depths of the universe with their varied, everlasting and restless motion, that this is the one world and heaven to have been created, and that all those particles of matter outside it do nothing. Moreover, nothing in the universe is the only one of its kind to be born and to grow, as opposed to belonging to some species, with many members of the same kind. Focus your mind first on animals. You will find that the wild beasts of the mountains, the human race, the speechless swarms of scaly fish, and all flying creatures, have such an origin. Therefore we must likewise admit that heaven, earth, sun, moon, sea, and all other existing things, are not unique but, rather, countless in number. (tr. Long & Sedley)