The Greek proper noun Petros (Πέτρος) is the name Jesus gave to Simon bar Jonah (John 1:42). The name means 'stone' or 'rock' and is a Greek translation of the Aramaic Kepha (Cephas). Petros typically denotes a movable stone or large rock, while petra (G4073) denotes bedrock. The distinction is important to the Matthew 16:18 debate, though the names were used somewhat interchangeably in Koine Greek.
The renaming of Simon to Petros is one of Jesus' most significant prophetic acts. In John 1:42, Jesus 'looked at him and said, You are Simon son of John. You will be called Cephas.' The future tense is prophetic — Simon must become what he is named. The Matthew 16:18 passage is pivotal: 'You are Petros (Peter), and on this rock (petra) I will build my church.' Whether petra refers to Peter himself, to his confession, or to Christ is debated — but all interpretations agree that Peter's confession of Jesus as Messiah is the defining moment. Peter's journey from denial to apostolic courage embodies the biblical truth that God transforms the unstable into pillars of His church.