An ellipsis is when a word or phrase is left out by the speaker/writer but is clearly implied.
I finished the race second, and he first. [i.e. …and he finished first.]
I wanted the green one, not the red. [i.e. …I did not want the red one.]
Who broke the window? I did. [i.e. …I did break the window.]
(Matt 20:28) ὥσπερ ὁ υἱὸς τοῦ ἀνθρώπου οὐκ ἦλθεν διακονηθῆναι ἀλλὰ διακονῆσαι καὶ δοῦναι τὴν ψυχὴν αὐτοῦ λύτρον ἀντὶ πολλῶν [i.e. …ἀλλὰ ὁ υἱὸς τοῦ ἀνθρώπου ἦλθεν διακονῆσαι καὶ δοῦναι τὴν ψυχὴν αὐτοῦ λύτρον ἀντὶ πολλῶν.]