John 1:23

ἔφη· ἐγὼ φωνὴ βοῶντος ἐν τῇ ἐρήμῳ· εὐθύνατε τὴν ὁδὸν κυρίου, καθὼς εἶπεν Ἡσαΐας ὁ προφήτης.

ἔφη verb imperfect active indicative 3rd singular from φημί (I say) "He said"

ἐγὼ pronoun 1st person singular "I"

φωνὴ noun nominative feminine singular "voice"

βοῶντος participle present active genitive masculine singular from βοάω (I cry out) "of one crying out"

ἐν preposition dative "in"

τῇ definite article dative feminine singular "the"

ἐρήμῳ noun dative feminine singular "wilderness/desert"

εὐθύνατε verb aorist active imperative 2nd plural from εὐθύνω (I make straight) "you all make straight"

τὴν definite article accusative feminine singular "the"

ὁδὸν noun accusative feminine singular "way"

κυρίου noun genitive masculine singular "of the lord"

καθὼς compound adverb "also as/even as"

εἶπεν verb aorist active indicative 3rd singular from εἶπον (I say) "he said"

Ἡσαΐας proper noun nominative masculine singular "Isaiah" (note: appositive)

ὁ definite article nominative masculine singular "the"

προφήτης noun nominative masculine singular "prophet"

Rough Word-by-word:
He said I the voice of one crying out in the wilderness you all make straight the way of the Lord even as he said Isaiah the prophet

Smooth Translation:
He said, "I am the voice of one crying out in the wilderness, 'Make straight the way of the Lord!' as the prophet Isaiah said."