What is the greek word for junior?

There isn't a single, direct Greek word translation for "junior" in the sense of indicating a younger person with the same name as their father. The concept is handled differently. You would typically use descriptive phrases instead, such as:

* ὁ νεώτερος (ho neōteros): This means "the younger one." You'd use this along with the name, e.g., "Δημήτριος ὁ νεώτερος" (Dēmētrios ho neōteros) meaning "Demetrius the younger."

* ὁ υἱός (ho huios): This means "the son." Again, you'd need to use this in conjunction with the father's name to clarify, potentially with a further clarifying phrase like νεώτερος.

Therefore, there's no single word equivalent, but rather a periphrastic expression is needed depending on the context.