Matthew 5...Salt and light. Earth vs the world.

γης:
Thayer Definition:
1) arable land
2) the ground, the earth as a standing place
3) the main land as opposed to the sea or water
4) the earth as a whole
4a) the earth as opposed to the heavens
4b) the inhabited earth, the abode of men and animals
5) a country, land enclosed within fixed boundaries, a tract of land, territory, region

κοσμου:
Thayer Definition:
1) an apt and harmonious arrangement or constitution, order, government
2) ornament, decoration, adornment, i.e. the arrangement of the stars, ‘the heavenly hosts’, as the ornament of the heavens. 1Pe_3:3
3) the world, the universe
4) the circle of the earth, the earth
5) the inhabitants of the earth, men, the human family
6) the ungodly multitude; the whole mass of men alienated from God, and therefore hostile to the cause of Christ
7) world affairs, the aggregate of things earthly
7a) the whole circle of earthly goods, endowments riches, advantages, pleasures, etc, which although hollow and frail and fleeting, stir desire, seduce from God and are obstacles to the cause of Christ
8) any aggregate or general collection of particulars of any sort
8a) the Gentiles as contrasted to the Jews (Rom_11:12 etc)
8b) of believers only, Joh_1:29; Joh_3:16; Joh_3:17; Joh_6:33; Joh_12:47 1Co_4:9; 2Co_5:19