Seinen

Seinen: young man

青年　ーー　n.

Hint: I think most people know this word when it comes to manga's genre but saying 'seinen' seems more into 'young adult' to differ it from shounen. See also: shoujo, shounen, josei, dansei

Sekai

sekai: (1) the world (2) society

世界 -- n.

Hint: ever heard a drama title called 'Sekai no Chuushin de Ai wo Sakebu' a.k.a Sekachu? It is well known translated as Crying out Love, in the Centre of the World.