Baseball has long been my sport of choice. In my school age years, I played other sports with friends in their yards or driveways, but only pursued baseball at a competitive level. As a result, it was not until college that I learned the rules of how to play basketball and football.
I can remember several weeks where my roommates and I were playing basketball and aside from knowing I needed to hustle and “get open,” I had no clue what was happening. My teammates would tell me to “run the court” or “block out” or “set a pick,” and I stumbled and faked my way along until I could learn how to play the game. I was eager to play hard and help my team to win, but I lacked an understanding of the terms for playing.
When it comes to considering the work and needs of missions, many of us would be helped to acknowledge that we need a greater understanding of the terms. We know the Great Commission, support and practice evangelism, and even advocate for the missionary task. Yet, often “missions” to us is like a game we enjoy watching but don’t know how to play.
So, during this time when many churches are focusing on their annual Global Missions giving, I present here some basic definitions of 5 crucial missiological terms. Some of these are elementary and well-known, but for the exercise of building a team where everyone knows the terms and how to play together, I hope you will find this review helpful.
1. Missionary. John Piper provides a helpful classification of two types of missionaries found in the Bible: the Timothy-type missionary and the Paul-type missionary. He explains, “We call Timothy a missionary because he left home (Lystra, Acts 16:1), joined a traveling team of missionaries, crossed cultures, and ended up overseeing the younger church in Ephesus (1 Tim 1:3) far from his homeland.”
The Timothy-type missionary, however, stays on the mission field in the same location even after churches are started and established.
The Paul-type missionary “was driven by a passion to make God’s name known among all the unreached peoples of the world. He never stayed in a place long, once the church was established.” The pursuit of traveling to places where there is no or little knowledge of Jesus Christ (Rom 15:20) distinguishes this type of missionary.
Whether they stay in one place or continue onward to other frontier areas, a missionary is one who crosses cultures to share the gospel.
2. Nations. The Bible records that nations were first created by God in response to the construction of the Tower of Babel (Gen 11). Previously having one language, the people were dispersed throughout the earth with distinct languages. The nations, both the Jewish nation and all Gentile nations, continue as central entities in the plan of God to display His glory and work out salvation and judgment.
It was to the nation of Israel that God sent his son, Jesus Christ, as Messiah to “suffer and rise from the dead the third day, that repentance for forgiveness of sins would be proclaimed in His name to all the nations” (Lk 24:47, emphasis mine). It is the commission of Christian churches (Mt 16:18) to continue the task of taking the message of God’s plan of salvation (Rom 10:14-15) to those nations who have not heard (Rom 15:21).
This message will be proclaimed by God’s children to the nations until the end of the world (Mt 24:14). At that time, the Messiah will return to the earth and all nations will submit to his rule and reign (Phil 2:10-11). People from every nation will worship him (Rev 7:9).
Piper helps us again here by reminding that the task of missions is “not just reaching more and more people but more and more peoples—tribes, tongues, peoples, nations.” When we understand this biblical definition of the nations (and the prescribed task to reach them) we are encouraged to know that the task of reaching all nations is finishable, for “the task is finishable because while the number of individual people keeps growing and changing, the number of people groups (by and large) does not.”
3. Reached and Unreached. In Romans 15:19, Paul says, “From Jerusalem and all the way around to Illyricum I have fulfilled the ministry of the gospel of Christ.” In 15:23, he explains that he no longer has “any room for work in these regions.” What Paul is essentially saying is, “The furthest east I have ever been is Jerusalem, and the furthest west I have ever been is Illyricum. And everywhere in between—in all the places I have been—the ministry has been fulfilled.” He has fully preached the gospel of Christ.
The idea here is not that every person in that region, as big as it is, is now a Christian. We know that is not the case. But he is saying that all the people in this region now have access to the gospel. He has sown seeds, and churches have sprouted up, and there are preachers there who will continue the work so that everyone in this huge region now has access to the gospel. The gospel has been preached here, the ministry has been fulfilled, and it’s now self-sustaining. In our language today we would call this region “reached” and “no longer unreached.”
In missions, most define a people group as reached when “there is an indigenous church able to evangelize the group.” However, there is ongoing discussion about at what point an indigenous church is “able.” That is, what percentage of the population of the people group is needed eventually to achieve the status of reached? Missiologists Zane Pratt, David Sills, and Jeff Walters, in Introduction to Global Missions, follow the common classification of a people group being reached when evangelicals consists of more than 2% of the population.
However, former missionary and fellow missiologist Robin Hadaway recently argued that setting the reached line at 2% is too low and hinders the healthy establishment of churches in a newly-reached area. He recommends raising the threshold back to 10-20%, and along with that, sending more missionaries to these areas previously thought of as reached. While that is a fruitful and important discussion, there is agreement at least that people groups with less than 2% evangelicals are clearly “unreached.”
4. The 10/40 Window. Unreached people groups exist in just about every country of the world, but they are most concentrated in what’s been called the 10/40 Window. Here’s a brief explanation of that term:
The 10/40 Window is an imaginary box that encloses an area of the globe from 10 degrees north of the equator to 40 degrees north of the equator, and from Northwest Africa to East Asia. Not only does this rectangle contain the majority of the world’s unreached lost; it is also home to three major religious blocs: Hinduism, Islam, and Buddhism; as well as areas of greatest poverty. 
The 10/40 Window
As this region represents such a high concentration of unreached peoples, churches and missionaries rightly focus on the 10/40 Window for preaching the gospel to “those who have never been told” of Jesus (Romans 15:21).
5. The Global South. In the later part of the 20th century, the largest populations of evangelicals around the world started from the historic West to shift South. The church is growing rapidly in Latin America, Africa, and Parts of Asia. “More Christians live there than in the United States, and they send out more missionaries than the United States and Western Europe.” As a result, churches and missionaries in the 21st century are having to increasingly adjust their thinking of the West as “reached.”
Certainly, there are more evangelicals still in the West compared to the 10/40 Window, but the rise of nominal Christianity and the uncertain commitments of the children and grandchildren of evangelicals mean that one day soon, if not already, the churches of the Global South will have need to send missionaries to the West.
As we gather in our churches and families to pray for the ongoing global work of the Great Commission, I hope this refesher of these basic and crucial terms will aid you in this biblically designed team task of seeing the earth filled with “the knowledge of the glory of the Lord as the waters cover the sea” (Hab 2:14).
At this time of year, the churches of the Southern Baptist Convention are focusing on their annual Global Missions Offering called the Lottie Moon Christmas Offering.  All gifts given toward this goal of $160 million go directly to missionaries serving on the field. Here is a helpful video and invitation from Jason K. Allen, president of Midwestern Seminary, about this offering.
This article is an adaptation of a portion of my chapter, “Pastor as Missionary,” that was my assignment in the new book edited by Jason K. Allen, Portraits of a Pastor (Moody Press, 2017). Here is more information about this new book:
Jason K. Allen, General Editor
Moody Press, 2017.
 John Piper, Brothers. We Are Not Professionals (B&H, 2013), 223.
 This paragraph is adapted from my forthcoming entry in the Worldview Study Bible (B&H, 2018).
 Piper, Brothers, 223.
 This paragraph is adapted from Jason G. Duesing’s, “A Plea for Ambitious Evangelicals,” in Union University Pulpit, (2013): 43-51.
 Piper, Let the Nations Be Glad! 3rd ed. (Baker, 2010), 217.
 Zane Pratt, M. David Sills, and Jeff K. Walters, Introduction to Global Missions (B&H, 2014), 27-30.
 Robin D. Hadaway, “A Course Correction in Missions: Rethinking the Two-Percent Threshold,” in SWJT 57:1 (Fall 2014).
 In fact, Pratt, Sills, and Walters, Introduction, 27-30, argue that for greatest accuracy, the term “unreached” needs further refinement into “unengaged unreached people groups” (UUPG) and “uncontacted unreached people groups” (UUUPG). The UUPGs are those groups with populations with less than 2% evangelicals and where no church planting has taken place among them for the last two years, and the UUUPGs are those groups hidden, hostile, or isolated with whom no contact has ever been made for gospel advance.
 Pratt, Sills, and Walters, Introduction, 30.
 Pratt, Sills, and Walters, Introduction,, 32.