What Is Written
The meaning of “worldly” is a matter of some controversy. This is true even among people strongly committed to Christian living as defined in Scripture. Most agree that “worldly” means being like the world and that being like the world isn’t good. But from there, confusion multiplies.
The reasons for this confusion are several. The most important for our purposes is that the meaning of “worldly” depends on the meaning “the world,” and many are confused regarding what “the world” means. What exactly is it that disciples of Christ should not be “like”? How much does it have to do with garments, music, hairstyles, or theaters?
In the NT, “world” usually translates one of three words: αἰών (aion), κόσμος (kosmos), and οἰκουμένη (oikoumene). All three vary in meaning depending on context. Of the three, oikoumene occurs the least frequently  and has the smallest range of meaning. In every case, it emphasizes the world as a place, sometimes with the focus on the people who live there. Jesus uses the word in Matthew 24:14. “This gospel of the kingdom will be preached in all the world.”  Luke uses oikoumene in Luke 2:1 where he describes a census of all the “inhabited earth.” The most negative occurrence of the word is probably Revelation 12:9, where John informs us that Satan deceives “the whole world.” Oikoumene is never the preferred word when writers want to identify “the world” as an evil believers should resist.
Of the two remaining words, kosmos and aion, the latter has the smaller range of meaning. It always has a strong time connotation and is normally translated “age,” “forever,” “eternity,” etc. Context sometimes gives aion the broader sense of all reality during a period of time. In these passages, its meaning is closer to “world” than “age.” Paul uses the word for the temporary wisdom and rulers “of this age” (1 Cor. 2:6). Hebrews 1:2 tells us that God “made the worlds [αἰῶνας, aions].” The epistles contain several strongly negative references to aion, such as Rom.12:2, “do not be conformed to this world.” Read more about What Does Worldly Look Like? Part 2