It may seem like we're splitting hairs to differentiate between "lost" and "unreached," but we aren't.
In a previous post, we discussed unreached peoples, who they are, and what it practically means to be unreached. The definition we gave for unreached was: "people groups among whom there is no indigenous community of believing Christians able to engage the people group with church planting." In describing what it would mean to be in an unreached people group (UPG), David Platt illuminates the one factor that makes a UPG different than merely being lost:
You don’t have access to the gospel. And this is key; this is why we don’t say, Well, I don’t know why we talk about unreached people around the world when there are unreached people who work at my office. Not true. Those people aren’t unreached. Why? Because they have access to the gospel. You are their access to the gospel!
The people who don't know Christ at your office are lost. For the salvation of their souls, they must respond to the gospel with repentance and faith. But because you are in their life (and, presumably, so are other Christians), they are not unreached.
While an individual can't be more or less lost (you either know Jesus or you don't), an individual can have more or less access to the gospel. For this reason, we talk about UPGs a lot.
We should always be sensitive to the lost, having eternity in our eyes and the good news on our lips. But when there are over 6,500 UPGSs comprised of at least 2 billion individual people… it's safe to say that the unreached deserve our urgent attention.