'World' in the Bible

Pure and undefiled religion before God and the Father is this: to visit orphans and widows in their affliction, to keep oneself unspotted from the world.

Hear, my beloved brethren: Has not God chosen the poor as to the world, rich in faith, and heirs of the kingdom, which he has promised to them that love him?

and the tongue is fire, the world of unrighteousness; the tongue is set in our members, the defiler of the whole body, and which sets fire to the course of nature, and is set on fire of hell.

Adulteresses, know ye not that friendship with the world is enmity with God? Whoever therefore is minded to be the friend of the world is constituted enemy of God.