I’ve been reading Thomas Aquinas on the Trinity lately. Here are some of the key terms.

Five notions

1. Innascibility (unbegottenness)
2. Paternity
3. Sonship
4. Common Spiration
5. Procession

Four relations

1. Paternity
2. Sonship
3. Common Spiration
4. Procession

Three persons

1. Father
2. Son/Word/Image
3. Holy Spirit/Love/Gift

Two processions

1. Generation
2. Spiration

One essence

1. The one divine nature