When it comes to particles and conjunctions especially, it can be difficult to translate every single one. Sometimes the best translation is punctuation, and other times it feels like the word is superfluous and should just be dropped in order to write in proper English.
But extreme caution is urged in the case of the later. There is a reason for every word, even if we don’t understand why it is used.
In Matthew 10 we find the list of the disciples. In v 10 we read, “Simon the Cananaean (Σίμων ὁ Καναναῖος), and Judas Iscariot (καὶ Ἰούδας ὁ Ἰσκαριώτης), who betrayed him (ὁ καὶ παραδοὺς αὐτόν).” ὁ … παραδοὺς αὐτόν is straight forward Greek, a phrase modifying Ἰούδας. But why is καὶ there, and should it be translated?