I'm not sure if it can be translated precisely in English.
It's a linking word (illustrative/explanatory link word) used to
~ give further information / explain something more / in other words
~ ASK for further information / confirmation
For example.
• Είμαι από την Ελλάδα, δηλαδή είμαι Ελληνίδα. I'm from Greece. In other words, I'm Greek.
• bla bla bla (excuses - and you were bored to listen to all this talking, so you ask:)........ Δηλαδή(/άρα) τι ώρα θα έρθεις; So, what time will you come?
• Είπα στην Μαρία, δηλαδή την αδερφή του Γιώργου, ότι θα αργήσω. I said to Maria, that is, George's sister, that I'm gonna be late.
• Δηλαδή;/Δηλαδή τι εννοείς; Meaning?/So what do you mean (exactly)? - If you didn't understand something....
• Δηλαδή(/άρα) πρέπει να φύγουμε τώρα; You mean(/So) we have to go now?
Ι hope this helps!! (^o^)/