The Greek Cross has its origins in ancient history. First, the church adopted the Latin Cross and Chi Rho through the Constantine's Labarum. Subsequently Julian removed both. When Justinian then came to power, he returned to using the cross, but began using what is known as the Greek Cross.
The Greek Cross is notable because all four arms are of equal length. This symmetry makes it easy to use in art, and it became popular in the Eastern Church.
Ultimately, the symbolism is the same as that of the Latin cross, symbolizing the crucifixion and resurrection of Jesus.
Greek Crosses are easy to find in art, and in particular in painting, because of their symmetry. Like Celtic Crosses, they have also become popular in secular art. They are frequently combined with other symbols, and can also be seen in a nimbus accompanying any person of the Trinity.
These are also popular in the furnishings that accompany worship spaces, and may be present on pulpits, fonts, pews or organs in some churches.
Here, it may be fun to explore a portion of scripture that isn't often studied in Bible Studies. First, briefly tell the legend of the Greek Cross and its adoption by Justinian. Highlight the fact that the Labarum was adopted by Constantine, but then removed by Julian, before Justinian adopted the Greek cross. In this legend, it is the powerful, the authorities who determined (or thought they determined) the use of symbols. Each time the authority changed, so did the symbols.
Now, read Jude 24-25. These verses are sometimes known as the Jude benediction. How does Jude view authority and power? When might we expect that to change?
Finally, ask participants where they have seen Greek crosses. See if you can find them in your church. Talk about why they may be beneficial in that setting.
If you have a Greek Cross permanently affixed in your worship space, it would be interesting to highlight it and discuss why it is there. Otherwise, relating the legend of Constantine, Julian, and Justinian may be an interesting way to talk about the enduring power of the Cross, and the strength of a tradition that transcends regimes and generations. Songs that fit this theme are abundant, and could tie into the sermon.
Because of its commonplace nature, the Greek Cross could fit easily at any point in ordinary time. Because it is a cross, it could work well during Holy Week as well