Segmentation is the missionary concept of discerning the basic social unit among a people along which the gospel will spread before it meets significant cultural barriers. These barriers are usually things like language, geography, culture, or religion. But there are many other factors that affect the transmission of the gospel. Political divisions, for example, can make it extremely difficult for one group to receive with good will any messenger from an opposing group. Social class can be deeply divisive, as can economic status, tribal affiliation, or racial prejudice. In urban centers, subcultural differences become increasingly isolating as people divide themselves into affinity, professional, and even virtual groups.
Of course, what seem like major barriers to the spread of the gospel are no obstacle for God. As he demonstrated in Acts 2, language can be overcome by His people on mission. In John 4, we see Jesus reaching across ethnic lines to proclaim Himself as the living water for Samaritans as well as the Jews. Paul took different approaches to sharing the gospel with tentmakers in the marketplace than he did with the philosophers in the forums. Peter had to be commanded in a vision to broaden his evangelism to include both Jews and gentiles. Throughout the book of Acts, we read not only of individuals coming to faith in Jesus, but also of entire households repenting and being baptized.
In every case, overcoming barriers is the work of God's sent people. The gospel meets us where we are, and we are discipled out of our preferences into God's mission. It isn't enough to enter a city and preach the gospel; we must identify the groups and work to make disciples across the social divides.