Charis means a gift, and the root of the word is 'pleasure'. Charis is a gift that gives pleasure. If it doesn't give pleasure, then it's not charis. For example an athlete or a great warrior gives charis through their excellent performance. We would say they are "full of grace" or "graceful". She gives the example of Achilles in the Illiad. Achillies wins the battle and so gives everyone charis (grace). In return he expects some charis back in the form of a share of the loot. But Agamemnon gives him only a tiny portion. Achilles goes off in a huff saying he hasn't received charis from Agamemnon. Agamemnon then sends him a huge share of loot, more than he would have got before, but now Achilles says because he's upset at the earlier humiliation, he takes no pleasure in it, so it doesn't constitute charis. So, charis must be received with pleasure or else it's not charis.

The aspect of charis that is even more fundamental to the concept is that it must be reciprocal. A bit like if you invite someone round to dinner, you expect to be invited round to dinner by them in return. So Achilles expected charis in return for the charis he gave everyone in fighting so well. To not give return-charis was truly scandalous in the Greek culture, even immoral.

In Romans, Paul talks about the grace of God and says, "What then? Shall we carry on sinning to increase grace all the more?" That would have been obviously false and scandalous to Greeks. If you get a gift, the response is not to beg for more, or increase your need for more grace, but instead to do what you can to give something back that will give pleasure to the one who gave you grace. This is embedded in the concept of charis and engrained in the culture. So we receive grace from God and it is expected that we will return to him something that gives him pleasure. This is not a payment for grace, because grace is a free gift, but in the Greek concept of grace, it would be absolutely expected. How do we give God pleasure? God delights in us when we grow up into Christ. When we glorify God through Christ in us.

One way the Greeks would do it was to sing praise songs for e.g. an athlete, to keep their name alive. I think this is where the tradition of Christian praise songs comes from. Since I read about this, when I sing at church I turn over in my mind the comparison of our praise songs for Christ to the forgotten praise songs of forgotten Greek heros. Christ's praise outlasts civilisations and peoples and will truly last forever!