We want to know the gospel well so that we can teach it to others with the intent to persuade them to trust Christ.

So we’ve demonstrated how to speak the gospel in six words.

And we’ve demonstrated how to speak the gospel in three minutes (I’ve timed it).

And now here is the gospel in one sentence:  Our sin is imputed to Christ and Christ’s righteousness is imputed to us so that we can enjoy God forever (2 Cor. 5:21).

And in fact, if you want to get the gospel to one word, it’s substitution (as explained in the previous sentence).